Question

我正在尝试在脑海中编译这个...我有一个带有firstname和lastname字段的表我有一个像“Bob Jones”或“Bob Michael Jones”等字符串。

事情是，我有例如鲍勃在名字，和迈克尔琼斯的姓氏

所以我想

SELECT neededfield, CONCAT(firstname, ' ', lastname) as firstlast 
  FROM users 
 WHERE firstlast = "Bob Michael Jones"

但它说未知专栏“firstlast”..任何人都可以帮忙吗？

Answer 1

您提供的别名用于查询的输出 - 它们在查询本身中不可用。

您可以重复表达式：

SELECT neededfield, CONCAT(firstname, ' ', lastname) as firstlast 
FROM users
WHERE CONCAT(firstname, ' ', lastname) = "Bob Michael Jones"

或包装查询

SELECT * FROM (
  SELECT neededfield, CONCAT(firstname, ' ', lastname) as firstlast 
  FROM users) base 
WHERE firstLast = "Bob Michael Jones"

Answer 2

试试这个：

SELECT * 
  FROM  (
        SELECT neededfield, CONCAT(firstname, ' ', lastname) as firstlast 
        FROM users 
    ) a
WHERE firstlast = "Bob Michael Jones"

Answer 3

SELECT needefield, CONCAT(firstname, ' ',lastname) as firstlast 
FROM users 
WHERE CONCAT(firstname, ' ', lastname) = "Bob Michael Jones"

Answer 4

使用CONCAT_WS（）。

SELECT CONCAT_WS(' ',firstname,lastname) as firstlast FROM users 
WHERE firstlast = "Bob Michael Jones";

第一个参数是其余参数的分隔符。

Answer 5

尝试：

SELECT neededfield, CONCAT(firstname, ' ', lastname) as firstlast 
  FROM users 
WHERE CONCAT(firstname, ' ', lastname) = "Bob Michael Jones"

除非您将查询作为子选择执行，否则您的别名firstlast在查询的where子句中不可用。

Answer 6

可以选择重复CONCAT表达式或使用子查询。您可以使用HAVING子句来识别列别名。

SELECT 
  neededfield, CONCAT(firstname, ' ', lastname) AS firstlast 
FROM
  users 
HAVING firstlast = "Bob Michael Jones"

这是一个有效的SQL Fiddle。

MySQL选择CONCAT条件

6 个答案: