从tbl1中未列出的tbl1中选择

Question

I need to make MySQL query to select records from TBL1 not listed in TBL2 , but not working with my query.

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

You need to change = NULL to IS NULL at the end; that's the correct syntax. See working with NULL values .