使用 'LIKE' 和 SQL 子查询的结果

Question

以下查询对我来说绝对没问题：

SELECT * From Customers
WHERE Customers.ContactName = (SELECT FirstName
                               FROM Employees as E, orders as O
                               WHERE <condition>
                               LIMIT 1);

但是，如果我使用 LIKE 而不是 = 来与子查询的结果进行比较，我不会得到任何结果。如何在上述查询中使用 LIKE '%%'？

Answer 1

我想这应该适合你，不是吗？

SELECT * From Customers
WHERE Customers.ContactName LIKE '%' + (
        SELECT FirstName from Employees as E, orders as O
        WHERE <condition>
        LIMIT 1
    ) + '%';

Answer 2

首先，这个查询应该不能正常工作：

SELECT *
From Customers
WHERE Customers.ContactName = (SELECT FirstName
                               from Employees as E, orders as O
                               WHERE LIMIT 1);

因为WHERE LIMIT 1不合适SQL。而且，您应该学会使用正确的 join 语法。据推测，您打算：

SELECT c.*
From Customers c
WHERE c.ContactName = (SELECT FirstName
                       FROM Employees as E JOIN
                            Orders as O
                            ON . . .
                       LIMIT 1
                      );

您可以想象在子查询中添加 LIKE 而不是 = 和 '%'：

WHERE c.ContactName LIKE (SELECT CONCAT('%', FirstName, '%') . . .

但我会使用 EXISTS:

来写这个

SELECT c.*
From Customers c
WHERE EXISTS (SELECT 1
              FROM Employees as E JOIN
                   Orders as O
                   ON . . .
              WHERE c.ContactName LIKE CONCAT('%', FirstName, '%')
             );

这与您的查询不完全相同。它做了一些更合理的事情。它不是比较子查询中的一个随机名称，而是确定子查询中是否有 any 匹配项。这似乎是一个更合理的查询意图。

Answer 3

SQL 服务器

这将 return 特定关键字

select * 
from Customers
where Customers.ContactName like (select top 1 FirstName from Employees )

这将 return 如果关键字存在

select * 
from Customers
where Customers.ContactName like '%' + (select top 1 FirstName from Employees) + '%'

Answer 4

我建议：

SELECT * From Customers as a
INNER JOIN (SELECT '%'+FirstName+'%' as FirstName from Employees as E, orders as O
                               WHERE <condition>
                               LIMIT 1) as b
ON a.ContactName LIKE b.Firstname;

Answer 5

如果你有员工的外键 table 那么你不需要使用 LIKE。但是，如果您想使用它，可以尝试关注

select * 
from customers a, employees b 
where (contions on employees) 
  and customers.contactname like '%'||b.firstname||'%';

Answer 6

使用您的方法，您需要用“%”将 FirstName 字段的两边括起来，以便将通配符放入您选择的值中。

所以，像

SELECT * From Customers 
 WHERE Customers.ContactName LIKE (SELECT '%' + FirstName + '%'
                                    from Employees as E
                                   inner join, orders as O on...
                                   WHERE <condition>
                                   LIMIT 1);

在我看来你最好加入你的桌子。也许这样会更好

SELECT c.* 
  FROM Customers c
 INNER JOIN Employees e on c.ContactName like '%' + e.FirstName + '%'
 WHERE <condition>

Answer 7

下面的查询是MSSQL语句，我用CHARINSDEX代替了LIKE。尝试 MySQL 中的相关函数（检查 INSTR 函数）而不是 CHARINDEX.

SELECT
    *
FROM
    Customers
WHERE
    CHARINDEX(( SELECT  TOP 1 FirstName
                FROM    Employees as E, orders as O
                WHERE   <condition>
                ), Customers.ContactName, 1
             ) > 0;

我不确定，但您可以在 MySQL.

中尝试以下操作

SELECT
    *
FROM
    Customers
WHERE
    INSTR(Customers.ContactName,
          ( SELECT  FirstName
            FROM    Employees as E, orders as O
            WHERE   <condition>
            LIMIT 1)) > 0;

Answer 8

为什么不用简单的 INNER JOIN:

SELECT Customers.*
FROM Customers
INNER JOIN Employees ON Customers.ContactName LIKE CONCAT('%', Employees.FirstName,'%')
WHERE Employees.Foo = 'Bar'

注意：+是加法运算符，不能用于连接字符串。

使用 'LIKE' 和 SQL 子查询的结果

Using 'LIKE' with the result of a SQL subquery

mysql

sql

subquery

sql-like