mysql 里面的isnull()和ifnull() is null 和 is not null
2016-10-17 18:24
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usergrade表
2.找到里面username是null的行
SELECT * FROM usergrade WHERE ISNULL(USERNAME)
SELECT * FROM usergrade WHERE USERNAME IS NULL
3.找到里面username不是null的行
SELECT * FROM usergrade WHERE USERNAME IS NOT NULL
4.列出所有的行,并且将username是null的字段替换为lxy
SELECT IFNULL(USERNAME,'lxy'),GRADE FROM usergrade
resource:/Uploads/Images/Content/201610/e7b35d5c32733b62bf5640c3fd4153a8
2.找到里面username是null的行
SELECT * FROM usergrade WHERE ISNULL(USERNAME)
SELECT * FROM usergrade WHERE USERNAME IS NULL
3.找到里面username不是null的行
SELECT * FROM usergrade WHERE USERNAME IS NOT NULL
4.列出所有的行,并且将username是null的字段替换为lxy
SELECT IFNULL(USERNAME,'lxy'),GRADE FROM usergrade
resource:/Uploads/Images/Content/201610/e7b35d5c32733b62bf5640c3fd4153a8
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