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INTERSECT_ALL\n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"結果如下：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/f5/f5c6221e485649c39b99a2f5932442ae.jpeg","alt":null,"title":null,"style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":null,"fromPaste":true,"pastePass":true}},{"type":"heading","attrs":{"align":null,"level":1},"content":[{"type":"text","text":"五、集合運算的優先級","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"1.INTERSECT>UNION=EXCEPT","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"2.首先計算INTERSECT,然後從左到右的出現順序依次處理優先級的相同的運算。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"3.可以使用圓括號控制集合運算的優先級，它具有最高的優先級。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":1},"content":[{"type":"text","text":"六、特殊處理","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"1.只有ORDER BY能夠直接應用於集合運算的結果；","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"2.其他階段如表運算符、WHERE、GROUP BY、HAVING等，不支持直接應用於集合運算的結果，這個時候可以使用表表達式來避開這一限制。如根據包含集合運算的查詢定義個表表達式，然後在外部查詢中對錶表達式應用任何需要的邏輯查詢處理；","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"3.ORDER BY字句不能直接應用於集合運算中的單個查詢，這個時候可以TOP+ORDER BY字句+表表達式來避開這一限制。如定義一個基於該TOP查詢的表表達式，然後通過一個使用這個表表達式的外部查詢參與集合運算。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":1},"content":[{"type":"text","text":"七、練習題","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"1.寫一個查詢，返回在2008年1月有訂單活動，而在2008年2月沒有訂單活動的客戶和僱員。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"期望結果：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/91/91cb257735bd5caad4d7ae7ee5d364d3.jpeg","alt":null,"title":null,"style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"方案一：EXCEPT","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（1）先用查詢1查詢出2008年1月份有訂單活動的客戶和僱員","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（2）用查詢2查詢2008年2月份客戶的訂單活動的客戶和僱員","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（3）用差集運算符查詢2008年1月有訂單活動而2008年2月沒有訂單活動的客戶和僱員","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"sql"},"content":[{"type":"text","text":"SELECT custid ,\n empid\nFROM Sales.Orders\nWHERE orderdate >= '20080101'\n AND orderdate < '20080201'\nEXCEPT\nSELECT custid ,\n empid\nFROM Sales.Orders\nWHERE orderdate >= '20080201'\n AND orderdate < '20080301'\n``` sql\n\n**方案二：NOT EXISTS**\n\n必須保證custid，empid不能爲null，才能用NOT EXISTS進行查詢，如果custid或empid其中有null值存在，則不能用NOT EXISTS進行查詢，因爲比較NULL值的結果是UNKNOWN，這樣的行用NOT EXISTS查詢返回的子查詢的行會被過濾掉，所以最後的外查詢會多出NULL值的行，最後查詢結果中會多出NULL值的行。\n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"SELECT custid ,empidFROM Sales.Orders AS O1WHERE orderdate >= '20080101'AND orderdate < '20080201'AND NOT EXISTS ( SELECT *FROM Sales.OrdersWHERE orderdate >= '20080201'AND orderdate < '20080301'AND custid = o1.custidAND empid = o1.empid )ORDER BY O1.custid ,","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"text"},"content":[{"type":"text","text":" O1.empid\n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"sql"},"content":[{"type":"text","text":"\n如果我往Sales.Orders表中插入兩行數據：\n\n插入cutid=NULL,empid=1,orderdate='20080101'\n``` sql\nINSERT INTO [TSQLFundamentals2008].[Sales].[Orders]\n ( [custid] ,\n [empid] ,\n [orderdate] ,\n [requireddate] ,\n [shippeddate] ,\n [shipperid] ,\n [freight] ,\n [shipname] ,\n [shipaddress] ,\n [shipcity] ,\n [shipregion] ,\n [shippostalcode] ,\n [shipcountry]\n )\nVALUES ( NULL ,\n 1 ,\n '20080101' ,\n '20080101' ,\n '20080101' ,\n 1 ,\n 1 ,\n 'A' ,\n '20080101' ,\n 'A' ,\n 'A' ,\n 'A' ,\n 'A'\n )\nGO\n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"插入cutid=NULL,empid=1,orderdate='20080201'","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"sql"},"content":[{"type":"text","text":"INSERT INTO [TSQLFundamentals2008].[Sales].[Orders]\n ( [custid] ,\n [empid] ,\n [orderdate] ,\n [requireddate] ,\n [shippeddate] ,\n [shipperid] ,\n [freight] ,\n [shipname] ,\n [shipaddress] ,\n [shipcity] ,\n [shipregion] ,\n [shippostalcode] ,\n [shipcountry]\n )\nVALUES ( NULL ,\n 1 ,\n '20080201' ,\n '20080101' ,\n '20080101' ,\n 1 ,\n 1 ,\n 'A' ,\n '20080101' ,\n 'A' ,\n 'A' ,\n 'A' ,\n 'A'\n )\nGO\n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"用方案一查詢出來結果爲50行，會把cutid=NULL,empid=1的行過濾掉","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"用方案二查詢出來結果爲51行，不會把cutid=NULL,empid=1的行過濾掉","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"用下面的方案可以解決上面的問題，需要處理cutid=NULL,或者empid=null的情況。返回50行","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"sql"},"content":[{"type":"text","text":"SELECT custid ,\n empid\nFROM Sales.Orders AS O1\nWHERE orderdate >= '20080101'\n AND orderdate < '20080201'\n AND NOT EXISTS ( SELECT *\n FROM Sales.Orders\n WHERE orderdate >= '20080201'\n AND orderdate < '20080301'\n AND ( custid = o1.custid\n AND empid = o1.empid\n )\n OR ( o1.custid IS NULL\n AND custid IS NULL\n AND empid = o1.empid\n )\n OR ( o1.custid IS NULL\n AND custid IS NULL\n AND o1.empid IS NULL\n AND custid IS NULL\n )\n OR ( custid = o1.custid\n AND o1.empid IS NULL\n AND custid IS NULL\n ) )\n","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"2.寫一個查詢，返回在2008年1月和在2008年2月都有訂單活動的客戶和僱員。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"期望結果：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/9a/9a625d5180d419149800d97adfe234bc.jpeg","alt":null,"title":null,"style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"方案一：INTERSECT","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（1）先用查詢1查詢出2008年1月份有訂單活動的客戶和僱員","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（2）用查詢2查詢2008年2月份客戶的訂單活動的客戶和僱員","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（3）用交集運算符查詢2008年1月和2008年2月都有訂單活動的客戶和僱員","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"sql"},"content":[{"type":"text","text":"SELECT custid ,\n empid\nFROM Sales.Orders\nWHERE orderdate >= '20080101'\n AND orderdate < '20080201'\nINTERSECT\nSELECT custid ,\n empid\nFROM Sales.Orders\nWHERE orderdate >= '20080201'\n AND orderdate < '20080301'\n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"方案二：EXISTS","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"必須保證custid，empid不能爲null，才能用EXISTS進行查詢，如果custid或empid其中有null值存在，則不能用EXISTS進行查詢，因爲比較NULL值的結果是UNKNOWN，這樣的行用EXISTS查詢返回的子查詢的行會被過濾掉，所以最後的外查詢會少NULL值的行，最後查詢結果中會少NULL值的行。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"sql"},"content":[{"type":"text","text":"SELECT custid ,\n empid\nFROM Sales.Orders AS O1\nWHERE orderdate >= '20080101'\n AND orderdate < '20080201'\n AND EXISTS ( SELECT *\n FROM Sales.Orders\n WHERE orderdate >= '20080201'\n AND orderdate < '20080301'\n AND custid = o1.custid\n AND empid = o1.empid )\nORDER BY O1.custid ,\n O1.empid\n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"如果我往Sales.Orders表中插入兩行數據：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"插入cutid=NULL,empid=1,orderdate='20080101'","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"插入cutid=NULL,empid=1,orderdate='20080201'","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"用方案一查詢出來結果爲6行，不會把cutid=NULL,empid=1的行過濾掉","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"用方案二查詢出來結果爲5行，會把cutid=NULL,empid=1的行過濾掉","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"用下面的方案可以解決上面的問題，需要處理cutid=NULL,或者empid=null的情況。返回6行。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"sql"},"content":[{"type":"text","text":"SELECT custid ,\n empid\nFROM Sales.Orders AS O1\nWHERE orderdate >= '20080101'\n AND orderdate < '20080201'\n AND EXISTS ( SELECT *\n FROM Sales.Orders\n WHERE orderdate >= '20080201'\n AND orderdate < '20080301'\n AND ( custid = o1.custid\n AND empid = o1.empid\n )\n OR ( o1.custid IS NULL\n AND custid IS NULL\n AND empid = o1.empid\n )\n OR ( o1.custid IS NULL\n AND custid IS NULL\n AND o1.empid IS NULL\n AND custid IS NULL\n )\n OR ( custid = o1.custid\n AND o1.empid IS NULL\n AND custid IS NULL\n ) )\n","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"3.寫一個查詢，返回在2008年1月和在2008年2月都有訂單活動，而在2007年沒有訂單活動的客戶和僱員","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"期望結果：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/49/492a9b9c17156bd8a66a49c8920beec1.jpeg","alt":null,"title":null,"style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"方案一：INTERSECT + EXCEPT","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"sql"},"content":[{"type":"text","text":"SELECT custid ,\n empid\nFROM Sales.Orders\nWHERE orderdate >= '20080101'\n AND orderdate < '20080201'\nINTERSECT\nSELECT custid ,\n empid\nFROM Sales.Orders\nWHERE orderdate >= '20080201'\n AND orderdate < '20080301'\nEXCEPT\nSELECT custid ,\n empid\nFROM Sales.Orders\nWHERE orderdate >= '20070101'\n AND orderdate < '20080101'\n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"方案二：EXISTS + NOT EXISTS","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"sql"},"content":[{"type":"text","text":"SELECT custid ,\n empid\nFROM Sales.Orders AS O1\nWHERE orderdate >= '20080101'\n AND orderdate < '20080201'\n AND EXISTS ( SELECT *\n FROM Sales.Orders\n WHERE orderdate >= '20080201'\n AND orderdate < '20080301'\n AND ( custid = o1.custid\n AND empid = o1.empid\n )\n OR ( custid = o1.custid\n AND custid IS NULL\n AND empid = o1.empid\n )\n OR ( custid = o1.custid\n AND custid IS NULL\n AND empid = o1.empid\n AND custid IS NULL\n )\n OR ( custid = o1.custid\n AND empid = o1.empid\n AND custid IS NULL\n )\n OR ( custid = o1.custid\n AND custid IS NULL\n AND empid = o1.empid\n AND custid IS NULL\n ) )\n AND NOT EXISTS ( SELECT *\n FROM Sales.Orders\n WHERE orderdate >= '20070101'\n AND orderdate < '20080101'\n AND ( custid = o1.custid\n AND empid = o1.empid\n )\n AND ( custid = o1.custid\n AND empid = o1.empid\n )\n OR ( custid = o1.custid\n AND custid IS NULL\n AND empid = o1.empid\n )\n OR ( custid = o1.custid\n AND custid IS NULL\n AND empid = o1.empid\n AND custid IS NULL\n )\n OR ( custid = o1.custid\n AND empid = o1.empid\n AND custid IS NULL\n )\n OR ( custid = o1.custid\n AND custid IS NULL\n AND empid = o1.empid\n AND custid IS NULL\n ) )\nORDER BY O1.custid ,\n O1.empid\n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"參考資料：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"《SQL2008技術內幕：T-SQL語言基礎》","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"歡迎關注我的公衆號：「","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"悟空聊架構","attrs":{}}],"attrs":{}},{"type":"text","text":"」","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"作者簡介：8 年互聯網職場老兵｜全棧工程師｜90 後超級奶爸｜開源踐行者｜公衆號萬粉原創號主。藍橋簽約作者，著有《JVM 性能調優實戰》專欄，手寫了一套 7 萬字 SpringCloud 實戰總結和 3 萬字分佈式算法總結。歡迎關注我的公衆號「悟空聊架構」，免費獲取資料學習。","attrs":{}}]}],"attrs":{}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"italic","attrs":{}},{"type":"strong","attrs":{}}],"text":"我是悟空，努力變強，變身超級賽亞人！","attrs":{}}]}]}
詳解 SQL 的集合運算
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INTERSECT_ALL\n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"結果如下：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/f5/f5c6221e485649c39b99a2f5932442ae.jpeg","alt":null,"title":null,"style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":null,"fromPaste":true,"pastePass":true}},{"type":"heading","attrs":{"align":null,"level":1},"content":[{"type":"text","text":"五、集合運算的優先級","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"1.INTERSECT>UNION=EXCEPT","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"2.首先計算INTERSECT,然後從左到右的出現順序依次處理優先級的相同的運算。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"3.可以使用圓括號控制集合運算的優先級，它具有最高的優先級。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":1},"content":[{"type":"text","text":"六、特殊處理","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"1.只有ORDER BY能夠直接應用於集合運算的結果；","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"2.其他階段如表運算符、WHERE、GROUP BY、HAVING等，不支持直接應用於集合運算的結果，這個時候可以使用表表達式來避開這一限制。如根據包含集合運算的查詢定義個表表達式，然後在外部查詢中對錶表達式應用任何需要的邏輯查詢處理；","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"3.ORDER BY字句不能直接應用於集合運算中的單個查詢，這個時候可以TOP+ORDER BY字句+表表達式來避開這一限制。如定義一個基於該TOP查詢的表表達式，然後通過一個使用這個表表達式的外部查詢參與集合運算。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":1},"content":[{"type":"text","text":"七、練習題","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"1.寫一個查詢，返回在2008年1月有訂單活動，而在2008年2月沒有訂單活動的客戶和僱員。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"期望結果：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/91/91cb257735bd5caad4d7ae7ee5d364d3.jpeg","alt":null,"title":null,"style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"方案一：EXCEPT","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（1）先用查詢1查詢出2008年1月份有訂單活動的客戶和僱員","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（2）用查詢2查詢2008年2月份客戶的訂單活動的客戶和僱員","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（3）用差集運算符查詢2008年1月有訂單活動而2008年2月沒有訂單活動的客戶和僱員","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"sql"},"content":[{"type":"text","text":"SELECT custid ,\n empid\nFROM Sales.Orders\nWHERE orderdate >= '20080101'\n AND orderdate < '20080201'\nEXCEPT\nSELECT custid ,\n empid\nFROM Sales.Orders\nWHERE orderdate >= '20080201'\n AND orderdate < '20080301'\n``` sql\n\n**方案二：NOT EXISTS**\n\n必須保證custid，empid不能爲null，才能用NOT EXISTS進行查詢，如果custid或empid其中有null值存在，則不能用NOT EXISTS進行查詢，因爲比較NULL值的結果是UNKNOWN，這樣的行用NOT EXISTS查詢返回的子查詢的行會被過濾掉，所以最後的外查詢會多出NULL值的行，最後查詢結果中會多出NULL值的行。\n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"SELECT custid ,empidFROM Sales.Orders AS O1WHERE orderdate >= '20080101'AND orderdate < '20080201'AND NOT EXISTS ( SELECT *FROM Sales.OrdersWHERE orderdate >= '20080201'AND orderdate < '20080301'AND custid = o1.custidAND empid = o1.empid )ORDER BY O1.custid ,","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"text"},"content":[{"type":"text","text":" O1.empid\n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"sql"},"content":[{"type":"text","text":"\n如果我往Sales.Orders表中插入兩行數據：\n\n插入cutid=NULL,empid=1,orderdate='20080101'\n``` sql\nINSERT INTO [TSQLFundamentals2008].[Sales].[Orders]\n ( [custid] ,\n [empid] ,\n [orderdate] ,\n [requireddate] ,\n [shippeddate] ,\n [shipperid] ,\n [freight] ,\n [shipname] ,\n [shipaddress] ,\n [shipcity] ,\n [shipregion] ,\n [shippostalcode] ,\n [shipcountry]\n )\nVALUES ( NULL ,\n 1 ,\n '20080101' ,\n '20080101' ,\n '20080101' ,\n 1 ,\n 1 ,\n 'A' ,\n '20080101' ,\n 'A' ,\n 'A' ,\n 'A' ,\n 'A'\n )\nGO\n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"插入cutid=NULL,empid=1,orderdate='20080201'","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"sql"},"content":[{"type":"text","text":"INSERT INTO [TSQLFundamentals2008].[Sales].[Orders]\n ( [custid] ,\n [empid] ,\n [orderdate] ,\n [requireddate] ,\n [shippeddate] ,\n [shipperid] ,\n [freight] ,\n [shipname] ,\n [shipaddress] ,\n [shipcity] ,\n [shipregion] ,\n [shippostalcode] ,\n [shipcountry]\n )\nVALUES ( NULL ,\n 1 ,\n '20080201' ,\n '20080101' ,\n '20080101' ,\n 1 ,\n 1 ,\n 'A' ,\n '20080101' ,\n 'A' ,\n 'A' ,\n 'A' ,\n 'A'\n )\nGO\n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"用方案一查詢出來結果爲50行，會把cutid=NULL,empid=1的行過濾掉","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"用方案二查詢出來結果爲51行，不會把cutid=NULL,empid=1的行過濾掉","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"用下面的方案可以解決上面的問題，需要處理cutid=NULL,或者empid=null的情況。返回50行","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"sql"},"content":[{"type":"text","text":"SELECT custid ,\n empid\nFROM Sales.Orders AS O1\nWHERE orderdate >= '20080101'\n AND orderdate < '20080201'\n AND NOT EXISTS ( SELECT *\n FROM Sales.Orders\n WHERE orderdate >= '20080201'\n AND orderdate < '20080301'\n AND ( custid = o1.custid\n AND empid = o1.empid\n )\n OR ( o1.custid IS NULL\n AND custid IS NULL\n AND empid = o1.empid\n )\n OR ( o1.custid IS NULL\n AND custid IS NULL\n AND o1.empid IS NULL\n AND custid IS NULL\n )\n OR ( custid = o1.custid\n AND o1.empid IS NULL\n AND custid IS NULL\n ) )\n","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"2.寫一個查詢，返回在2008年1月和在2008年2月都有訂單活動的客戶和僱員。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"期望結果：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/9a/9a625d5180d419149800d97adfe234bc.jpeg","alt":null,"title":null,"style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"方案一：INTERSECT","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（1）先用查詢1查詢出2008年1月份有訂單活動的客戶和僱員","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（2）用查詢2查詢2008年2月份客戶的訂單活動的客戶和僱員","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（3）用交集運算符查詢2008年1月和2008年2月都有訂單活動的客戶和僱員","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"sql"},"content":[{"type":"text","text":"SELECT custid ,\n empid\nFROM Sales.Orders\nWHERE orderdate >= '20080101'\n AND orderdate < '20080201'\nINTERSECT\nSELECT custid ,\n empid\nFROM Sales.Orders\nWHERE orderdate >= '20080201'\n AND orderdate < '20080301'\n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"方案二：EXISTS","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"必須保證custid，empid不能爲null，才能用EXISTS進行查詢，如果custid或empid其中有null值存在，則不能用EXISTS進行查詢，因爲比較NULL值的結果是UNKNOWN，這樣的行用EXISTS查詢返回的子查詢的行會被過濾掉，所以最後的外查詢會少NULL值的行，最後查詢結果中會少NULL值的行。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"sql"},"content":[{"type":"text","text":"SELECT custid ,\n empid\nFROM Sales.Orders AS O1\nWHERE orderdate >= '20080101'\n AND orderdate < '20080201'\n AND EXISTS ( SELECT *\n FROM Sales.Orders\n WHERE orderdate >= '20080201'\n AND orderdate < '20080301'\n AND custid = o1.custid\n AND empid = o1.empid )\nORDER BY O1.custid ,\n O1.empid\n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"如果我往Sales.Orders表中插入兩行數據：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"插入cutid=NULL,empid=1,orderdate='20080101'","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"插入cutid=NULL,empid=1,orderdate='20080201'","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"用方案一查詢出來結果爲6行，不會把cutid=NULL,empid=1的行過濾掉","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"用方案二查詢出來結果爲5行，會把cutid=NULL,empid=1的行過濾掉","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"用下面的方案可以解決上面的問題，需要處理cutid=NULL,或者empid=null的情況。返回6行。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"sql"},"content":[{"type":"text","text":"SELECT custid ,\n empid\nFROM Sales.Orders AS O1\nWHERE orderdate >= '20080101'\n AND orderdate < '20080201'\n AND EXISTS ( SELECT *\n FROM Sales.Orders\n WHERE orderdate >= '20080201'\n AND orderdate < '20080301'\n AND ( custid = o1.custid\n AND empid = o1.empid\n )\n OR ( o1.custid IS NULL\n AND custid IS NULL\n AND empid = o1.empid\n )\n OR ( o1.custid IS NULL\n AND custid IS NULL\n AND o1.empid IS NULL\n AND custid IS NULL\n )\n OR ( custid = o1.custid\n AND o1.empid IS NULL\n AND custid IS NULL\n ) )\n","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"3.寫一個查詢，返回在2008年1月和在2008年2月都有訂單活動，而在2007年沒有訂單活動的客戶和僱員","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"期望結果：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/49/492a9b9c17156bd8a66a49c8920beec1.jpeg","alt":null,"title":null,"style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"方案一：INTERSECT + EXCEPT","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"sql"},"content":[{"type":"text","text":"SELECT custid ,\n empid\nFROM Sales.Orders\nWHERE orderdate >= '20080101'\n AND orderdate < '20080201'\nINTERSECT\nSELECT custid ,\n empid\nFROM Sales.Orders\nWHERE orderdate >= '20080201'\n AND orderdate < '20080301'\nEXCEPT\nSELECT custid ,\n empid\nFROM Sales.Orders\nWHERE orderdate >= '20070101'\n AND orderdate < '20080101'\n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"方案二：EXISTS + NOT EXISTS","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"sql"},"content":[{"type":"text","text":"SELECT custid ,\n empid\nFROM Sales.Orders AS O1\nWHERE orderdate >= '20080101'\n AND orderdate < '20080201'\n AND EXISTS ( SELECT *\n FROM Sales.Orders\n WHERE orderdate >= '20080201'\n AND orderdate < '20080301'\n AND ( custid = o1.custid\n AND empid = o1.empid\n )\n OR ( custid = o1.custid\n AND custid IS NULL\n AND empid = o1.empid\n )\n OR ( custid = o1.custid\n AND custid IS NULL\n AND empid = o1.empid\n AND custid IS NULL\n )\n OR ( custid = o1.custid\n AND empid = o1.empid\n AND custid IS NULL\n )\n OR ( custid = o1.custid\n AND custid IS NULL\n AND empid = o1.empid\n AND custid IS NULL\n ) )\n AND NOT EXISTS ( SELECT *\n FROM Sales.Orders\n WHERE orderdate >= '20070101'\n AND orderdate < '20080101'\n AND ( custid = o1.custid\n AND empid = o1.empid\n )\n AND ( custid = o1.custid\n AND empid = o1.empid\n )\n OR ( custid = o1.custid\n AND custid IS NULL\n AND empid = o1.empid\n )\n OR ( custid = o1.custid\n AND custid IS NULL\n AND empid = o1.empid\n AND custid IS NULL\n )\n OR ( custid = o1.custid\n AND empid = o1.empid\n AND custid IS NULL\n )\n OR ( custid = o1.custid\n AND custid IS NULL\n AND empid = o1.empid\n AND custid IS NULL\n ) )\nORDER BY O1.custid ,\n O1.empid\n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"參考資料：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"《SQL2008技術內幕：T-SQL語言基礎》","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"歡迎關注我的公衆號：「","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"悟空聊架構","attrs":{}}],"attrs":{}},{"type":"text","text":"」","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"作者簡介：8 年互聯網職場老兵｜全棧工程師｜90 後超級奶爸｜開源踐行者｜公衆號萬粉原創號主。藍橋簽約作者，著有《JVM 性能調優實戰》專欄，手寫了一套 7 萬字 SpringCloud 實戰總結和 3 萬字分佈式算法總結。歡迎關注我的公衆號「悟空聊架構」，免費獲取資料學習。","attrs":{}}]}],"attrs":{}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"italic","attrs":{}},{"type":"strong","attrs":{}}],"text":"我是悟空，努力變強，變身超級賽亞人！","attrs":{}}]}]}
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