測試常用sql總結

1. sql中查找爲空的記錄，使用IS NULL和IS NOT NULL關鍵字

select * from database.table where row1 IS NULL
select * from database.table where row1 IS NOT NULL

2. 獲取數據表的列名等信息，也可以直接使用select * from information_schema.'COLUMNS’查看information.schema.'COLUMNS’表中都有什麼列名稱

select column_name from information_schema.'COLUMNS' where table_name = 'sql_table_name' and table_schema = 'db_name'

3. 從數據庫中隨機取幾個值，如下例子所示爲從t_securities表中隨機取三個security_id

select security_id from t_securities order by rand() limit 3

4. 獲取表中該列最大的值

select max(value_version) from t_config_item

5. 根據數據表中的值作字典轉換，如數據庫中保存’101’實際意義爲上交所，'102’實際意義爲深交所

select security_id,if(market_id='101','上海','深圳') from t_securities