mysql - 使用用户定义的变量指定列别名

Question

我想使用用户定义的变量重命名查询的列。

例如:

select id as @rt from table_name

Answer 1

这是不可能的。您必须动态创建 sql 字符串。

C#:

string columnName = "xy";
string sql = "SELECT id AS " + columnName + " FROM table_name";

VB:

Dim columnName As String = "xy"
Dim sql As String = "SELECT id AS " & columnName & " FROM table_name"

您也可以在 MySql 的存储过程中执行此操作。请参阅 MySql 文档以了解 SQL Syntax for Prepared Statements

它看起来像这样(未测试):

CREATE PROCEDURE myProc (columnName VARCHAR(30))
BEGIN
SET @sql = CONCAT("SELECT id AS ", columnName, " FROM table_name");
    PREPARE s1 FROM @sql;
    EXECUTE s1;
    DEALLOCATE PREPARE s1;
END$$