sql-server - 仅选择具有 NULL 值的列

Question

如何选择表中所有行仅包含 NULL 值的所有列？我正在使用MS SQL Server 2005。我试图找出表中未使用哪些列，以便删除它们。

Answer 1

这是 sql 2005 或更高版本:将 ADDR_Address 替换为您的表名。

declare @col varchar(255), @cmd varchar(max)

DECLARE getinfo cursor for
SELECT c.name FROM sys.tables t JOIN sys.columns c ON t.Object_ID = c.Object_ID
WHERE t.Name = 'ADDR_Address'

OPEN getinfo

FETCH NEXT FROM getinfo into @col

WHILE @@FETCH_STATUS = 0
BEGIN
    SELECT @cmd = 'IF NOT EXISTS (SELECT top 1 * FROM ADDR_Address WHERE [' + @col + '] IS NOT NULL) BEGIN print ''' + @col + ''' end'
    EXEC(@cmd)

    FETCH NEXT FROM getinfo into @col
END

CLOSE getinfo
DEALLOCATE getinfo