[英]How To Remove Before Filter SQL QUERY
我的查詢:
SELECT *
FROM tvn_Listing
LEFT JOIN tvn_ListingOption ON (tvn_Listing.id = tvn_ListingOption.listings_id
AND tvn_ListingOption.options_id = 12)
當我離開聯接兩個表時如何刪除空記錄? 我的查詢返回的結果不是條件指定的結果。
如果我正確理解了您的問題,那么問題是:
您可以從tvn_Listing
表中獲取記錄,這些記錄的LEFT JOIN
表tvn_ListingOption
值為NULL
。 好了,您可以在tvn_ListingOption
表中檢查空值,例如:
SELECT *
FROM tvn_Listing
LEFT JOIN tvn_ListingOption ON (tvn_Listing.id = tvn_ListingOption.listings_id
AND tvn_ListingOption.options_id = 12)
WHERE tvn_ListingOption.Id IS NOT NULL
請注意,在其中添加NOT NULL條件將影響結果(如果options_id為NULLABLE)
test=# select * from tvn_Listing;
id | nm
----+----
1 | A
2 | B
(2 rows)
test=# select * from tvn_listingoption ;
id | op
----+----
1 | A
3 | B
| D
(3 rows)
test=# select * from tvn_listing left join tvn_listingoption on tvn_listing.id=tvn_listingoption.id;
id | nm | id | op
----+----+----+----
1 | A | 1 | A
2 | B | |
(2 rows)
test=# select * from tvn_listing left join tvn_listingoption on tvn_listing.id=tvn_listingoption.id and tvn_listingoption.id is not null ;
id | nm | id | op
----+----+----+----
1 | A | 1 | A
2 | B | |
(2 rows)
test=# select * from tvn_listing left join tvn_listingoption on tvn_listing.id=tvn_listingoption.id where tvn_listingoption.id is not null ;
id | nm | id | op
----+----+----+----
1 | A | 1 | A
(1 row)
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