從tbl1中選擇未列在tbl2中

Question

我需要進行MySQL查詢以選擇TBL1中未列出的記錄，但未在TBL2中列出，但未處理我的查詢。

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

您需要更改= NULL到IS NULL末;這是正確的語法。請參閱working with NULL values。