posgresql中缺少表的FROM子句条目

Question

我正在学习数据库查询，并且遇到了一种情况，根据某些情况，我已经获得了现场

    select brandname 
    from shopping_men_women_fashion.shoppingbrandmaster 
    where shoppingbrandmaster.brandid =clothing.brandid

它抛出一个错误

 missing FROM-clause entry for table clothing.brandid

这个错误是关于什么的？

Answer 1

你错过了参加clothing Table

SELECT shoppingbrandmaster.brandname
FROM   shopping_men_women_fashion.shoppingbrandmaster,
       clothing
WHERE  shoppingbrandmaster.brandid = clothing.brandid 

要么

SELECT shoppingbrandmaster.brandname
FROM   shopping_men_women_fashion.shoppingbrandmaster
       JOIN clothing
         ON shoppingbrandmaster.brandid = clothing.brandid 

Answer 2

您可以使用表别名和USING简化语法：

SELECT s.brandname
FROM   shopping_men_women_fashion.shoppingbrandmaster s
JOIN   shopping_men_women_fashion.clothing            c USING (brandid);

我假设您的第二张表也存在于shopping_men_women_fashion模式中。 如果对一个表进行模式限定有意义，那么对另一个表进行模式限定有意义。

（在此示例中未引用clothing的列别名c ，可以将其删除。）