简单判断
当 status=1时返回1,不然0 :mysql
select id, if(status=1, 1, 0) as source from table_1
IF(表达式1, 表达式2 ,表达式3)
若是表达式1为true(表达式1 <> 0 and 表达式1 <> NULL), 返回表达式2;不然返回表达式3;至关于三目运算符web
mysql> SELECT IF(1>2,2,3); -> 3 mysql> SELECT IF(1<2,'yes','no'); -> 'yes'
多条件语句sql
select id, ( CASE WHEN qty_1 <= '23' THEN price WHEN '23' > qty_1 && qty_2 <= '23' THEN price_2 WHEN '23' > qty_2 && qty_3 <= '23' THEN price_3 WHEN '23' > qty_3 THEN price_4 ELSE 1 END ) AS total from product;