在执行块中具有多个SQL语句的Rails和MySQL语法错误 [英] Rails and MySQL syntax error with multiple SQL statements in an execute block

问题描述

在使用MySQL的应用程序的Rails迁移中，我具有以下代码:

I have the following code in a Rails migration for an app that uses MySQL:

execute <<-SQL
  ALTER TABLE properties
    ADD name VARCHAR(255) NOT NULL;

  ALTER TABLE properties
    ADD CONSTRAINT fk_properties_name
    FOREIGN KEY (name)
    REFERENCES valid_property_names (property_name);
SQL

运行迁移时，出现以下错误:

When I run the migration, I get the following error:

Mysql2::Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'ALTER TABLE properties

为什么会出现此错误以及如何解决?

Why am I getting this error and how do I fix it?

推荐答案

这里的问题是，当同一执行块中有多个SQL命令时，Rails Mysql2数据库适配器会阻塞.以下将正常运行:

The problem here is that the Rails Mysql2 database adapter chokes when there are multiple SQL commands within the same execute block. The following will run fine:

execute <<-SQL
  ALTER TABLE properties
    ADD name VARCHAR(255) NOT NULL;
SQL
execute <<-SQL
  ALTER TABLE properties
    ADD CONSTRAINT fk_properties_name
    FOREIGN KEY (name)
    REFERENCES valid_property_names (property_name);
SQL

如果您是将PostgreSQL与Rails一起使用，则此行为可能会使您感到困惑，因为Postgres适配器没有相同的限制.

This behavior may confuse you if you're coming from using PostgreSQL with Rails since the Postgres adapter doesn't have the same limitation.

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