关于mysql的 SELECT ... INTO 语法

关于mysql的 SELECT ... INTO 语法，当一行都没有取得到时，会引发warning。

以下是mysql在线文档的英文5.1版的说明。

原文：http://dev.mysql.com/doc/refman/5.1/en/select-into-statement.html

12.8.3.3. SELECT ... INTO Statement

SELECT col_name [, col_name] ...    INTO var_name [, var_name] ...    table_expr

SELECT ... INTO syntax enables selected columns to be stored directly into variables. The query should return a single row. If the query returns no rows, a warning with error code 1329 occurs (No data), and the variable values remain unchanged. If the query returns multiple rows, error 1172 occurs (Result consisted of more than one row). If it is possible that the statement may retrieve multiple rows, you can use LIMIT 1 to limit the result set to a single row.

SELECT id,data INTO x,y FROM test.t1 LIMIT 1;

User variable names are not case sensitive. See Section 8.4, “User-Defined Variables”.

In the context of SELECT ... INTO statements that occur as part of events executed by the Event Scheduler, diagnostics messages (not only errors, but also warnings) are written to the error log, and, on Windows, to the application event log. For additional information, see Section 19.4.5, “Event Scheduler Status”.