使用EXISTS的SQL语法错误

由于某种原因，当我尝试运行此SQL时出现语法错误。使用EXISTS的SQL语法错误

SELECT C.CUSTNUM 
FROM CUSTOMERS AS C 
WHERE C.CUSTNUM EXISTS (
    SELECT P.CNUM 
    FROM PURCHASES AS P 
    WHERE P.PNUM EXISTS (
     SELECT * 
     FROM PRODUCTS AS PR 
     WHERE PR.MSRP = 9.99))

我确定关闭了括号，但在查询表达式中仍然出现语法错误。在我的代码中可能有一些简单的东西。有任何想法吗？谢谢一堆。

来源

2016-09-26 Streamer

哪个RDBMS是这个呢？请添加一个标签来指定您是使用'mysql'，'postgresql'，'sql-server'，'oracle'还是'db2' - 或者其他的东西。 –

试试这个

SELECT C.CUSTNUM 
FROM CUSTOMERS AS C 
WHERE EXISTS (
    SELECT P.CNUM 
    FROM PURCHASES AS P 
    WHERE EXISTS (
     SELECT * 
     FROM PRODUCTS AS PR 
     WHERE PR.MSRP = 9.99))

来源

2016-09-26 22:29:13 Sher

当您使用EXISTS指定的子查询本身内的约束。如果子查询为给定条件C.CUSTNUM = P.CNUM返回至少一行，则认为条件满足。

我想这可以重写一个JOIN到PRODUCTS表。

SELECT C.CUSTNUM 
FROM CUSTOMERS AS C 
WHERE EXISTS (
    SELECT 1 
    FROM PURCHASES AS P 
    JOIN PRODUCTS AS PR ON 
     ON P.PNUM = PR.PNUM -- not sure what column to join on in PRODUCTS 
    WHERE 
     C.CUSTNUM = P.CNUM -- added the correlation, I believe this is what you mean 
     PR.MSRP = 9.99 
    )

如果不是这种情况，只要坚持到您的修改后的查询：

SELECT C.CUSTNUM 
FROM CUSTOMERS AS C 
WHERE EXISTS (
    SELECT 1 
    FROM PURCHASES AS P 
    WHERE 
     EXISTS (
     SELECT 1 
     FROM PRODUCTS AS PR 
     WHERE PR.MSRP = 9.99 
     ) 
     AND C.CUSTNUM = P.CNUM

但要注意的是，外部子查询将从PURCHASES返回所有行，如果有至少一个排PRODUCTS表无论任何列的匹配如何（您没有指定它们之间的任何相关条件）都有MSRP = 9.99。

来源

2016-09-26 22:32:19

使用的例子存在：

create table tab1(id1 number); 
create table tab2(id2 number); 
insert into tab1 values (1); 
insert into tab1 values (2); 
insert into tab2 values (2); 
select * 
from tab1 
where exists (select 1 
       from tab2 
       where tab2.id2 = tab1.id1 
      )

结果：2

注意，子查询相关，基于一些领域，这似乎是你需要做什么外一个。

来源

2016-09-26 22:32:25 Aleksej

我想你想使用，而不是EXISTS

SELECT C.CUSTNUM 
FROM CUSTOMERS AS C 
WHERE C.CUSTNUM IN (
    SELECT P.CNUM 
    FROM PURCHASES AS P 
    WHERE P.PNUM IN (
     SELECT PR.PNUM /* I'm unsure of the proper column here*/ 
     FROM PRODUCTS AS PR 
     WHERE PR.MSRP = 9.99))

来源

2016-09-26 22:41:49 SergeiBednar

使用EXISTS的SQL语法错误

回答

相关问题