MySQL选择条件条件

我正在尝试将其编译。.我有一个带有firstname和lastname字段的表，并且我有一个字符串，例如“ Bob Jones”或“ Bob Michael Jones”以及其他几个字符串。

事实是，例如我姓鲍勃，姓迈克尔·琼斯

所以我想

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

但是它说未知列“ firstlast” ..有人可以帮助吗？

您提供的别名用于查询的输出-它们本身在查询中不可用。

您可以重复表达：

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"

试试这个：

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

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

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。

尝试：

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

除非您以子选择方式进行查询，否则别名firstlast在查询的where子句中不可用。

有重复CONCAT表达式或使用子查询的替代方法。您可以使用该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。