sqlserver常用sql

1.求某个字段长度

SELECT
    MAX (DATALENGTH(content))
FROM
    mytable

2.查询数据库中所有表数据量

DECLARE @SQL VARCHAR(MAX)  
SELECT @SQL=ISNULL(@SQL+'  
UNION ALL ','')+'SELECT '''+NAME+''' AS TB,COUNT(1) AS TOTAL FROM ['+NAME+']'  
FROM SYS.TABLES  
EXEC (@SQL) 

• 3.case

SELECT
    CASE 
        WHEN STATE = 20     THEN '待发货'
        WHEN STATE = 30     THEN '已发货'
        WHEN STATE = 40     THEN '已收货'
ELSE '其他' END
FROM mall_order