如何筛选SQL查询

Question

我查询之前删除：

SELECT * 
FROM tvn_Listing 
LEFT JOIN tvn_ListingOption ON (tvn_Listing.id = tvn_ListingOption.listings_id 
           AND tvn_ListingOption.options_id = 12) 

如何删除空记录，当我离开的两个表？ 我的查询返回的结果不是条件指定的。

Answer 1

如果我理解你的问题正确的问题是：

你从tvn_Listing表具有不同于LEFT JOIN编表tvn_ListingOptionNULL值的记录。那么你可以在tvn_ListingOption表检查空值，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 

Answer 2

注意，如果您添加NOT NULL条件会影响效果（如果options_id为空）

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)