sql len函数 CASE WHEN

SELECT
    LEN('SQL Server LEN') length,
    LEN('SQL Server LEN   ') length_with_trailing_blanks;

SELECT
(CASE WHEN LEN('')=0 THEN  '001' ELSE '1线' END) --执行001
SELECT
(CASE WHEN LEN('1线')=0 THEN  '001' ELSE '1线' END) --执行1线