數據庫MySQL二

原創 爱说梦话的人 2020-05-07 00:59

注意拼接的時候如果爲null則都爲null

用if null

 

 

1、條件查詢

 

2、按邏輯表達式篩選

3、模糊查詢

還有not like

用轉義字符\

#2、in

 

 

數值型的常量值都不用單引號，非數值型的都用單引號

#3、between and

功能：判斷某個字段的值是不是介於XX之間

#4 is null

p268排序查詢

第二列就是first_name

 

 

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