如何检查MySQL中的列是否为空或空?

我在一个表中有一个列，它可能包含空值或空值。我如何检查一个列是否为空或空的行中存在的表?

(e.g. null or '' or '  ' or '      ' and ...)

当前回答

select * from table where length(RTRIM(LTRIM(column_name))) > 0

其他回答

如果你想在做ORDER BY时最后呈现NULL值，试试这个:

SELECT * FROM my_table WHERE NULLIF(some_col, '') IS NULL;

要么

SELECT IF(field1 IS NULL or field1 = '', 'empty', field1) as field1 from tablename

SELECT case when field1 IS NULL or field1 = ''
        then 'empty'
        else field1
   end as field1 from tablename

try

SELECT 0 IS NULL ,  '' IS NULL , NULL IS NULL

-> 0, 0, 1

SELECT ISNULL('  ') , ISNULL( NULL )
 -> 0 ,1

参考

SELECT column_name FROM table_name WHERE column_name IN (NULL, '')

你也可以

SELECT * FROM table WHERE column_name LIKE ''

逆存在

SELECT * FROM table WHERE column_name NOT LIKE ''

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