糾正:格式1的字段2後面應該有個‘逗号’
錯誤格式:
select 字段1,字段2
case 字段1
when 條件表達式1, then 結果表達式1
end
from 表
分層結構圖:
外層是selct * from 表的結構
裡層是case when結構
舉例1:
定義一個變量,當變量為2時輸出字元串’var is 2‘,當變量為1時輸出字元串’var is 1‘,當變量為不等于1和2時輸出字元串’var is not 1 or 2‘
DECLARE @var INT;
SET @var=2
select
CASE
WHEN @var=2 THEN 'var is'+convert(varchar(9),@var)
WHEN @var=1 THEN 'var is 1'
ELSE 'var is not 1 or 2'
END
舉例2:
輸出b等于1,2或其他值時的字元串
select b,
CASE b
WHEN '2' THEN 'var is 2'
WHEN '1' THEN 'var is 1'
ELSE 'var is not 1 or 2'
END
from t1
結果: