从tbl2中未列出的tbl1中选择

Question

我需要进行MySQL查询，以便从TBL2中未列出的TBL1中选择记录，但不使用我的查询。

SELECT deleted_guids.guid_type
     , HEX(data_table.guid_id) as guid_id
     , HEX(data_table.guid_type) as guid_type
FROM data_table 
LEFT JOIN deleted_guids 
     ON     data_table.guid_id = deleted_guids.guid_id 
        AND data_table.guid_type = deleted_guids.guid_type 
WHERE deleted_guids.guid_type = NULL;

Answer 1

最后需要将= NULL更改为IS NULL；这是正确的语法。参见working with NULL values。