php 将字符串与 MySQL 中的字段值连接起来
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Concatenate string with field value in MySQL
提问by Ben
I have the need to concatenate a string with a field value in a MySQL query in order to LEFT JOIN two tables.
我需要在 MySQL 查询中将一个字符串与一个字段值连接起来，以便 LEFT JOIN 两个表。
Table one has a column called "category_id" with numeric values, such as 61, 78, 94 and such.
表一有一个名为“category_id”的列，其中包含数字值，例如 61、78、94 等。
Table two has a column called "query" which refers to a request route mechanism, and it has values such as "product_id=68", "category_id=74", "manufacturer_id=99" and so on.
表二有一个名为“query”的列，它指的是一种请求路由机制，它有“product_id=68”、“category_id=74”、“manufacturer_id=99”等值。
So in my query I require to join the tables when ever a concatenated string derived from a set string and the value of the "category_id" column matches the query field.
因此，在我的查询中，当从集合字符串派生的连接字符串和“category_id”列的值与查询字段匹配时，我需要加入表。
My SQL statement is currently:
我的 SQL 语句目前是：
SELECT * FROM tableOne
LEFT JOIN tableTwo
ON tableTwo.query = 'category_id=' + tableOne.category_id
I have tried using the || operator instead of the + operator, but still no luck. Is it possible to do this in MySQL, or have I jumped the gun here?
我试过使用 || 运算符而不是 + 运算符，但仍然没有运气。是否可以在 MySQL 中执行此操作，或者我是否在这里过火了？
回答by Will Hannah
回答by chadzheng
SELECT ..., CONCAT( 'category_id=', tableOne.category_id) as query2 FROM tableOne
LEFT JOIN tableTwo
ON tableTwo.query = query2
回答by David Namenyi
Here is a great answer to that:
这是一个很好的答案：
SET sql_mode='PIPES_AS_CONCAT';
SET sql_mode='PIPES_AS_CONCAT';
Find more here: https://stackoverflow.com/a/24777235/4120319
在这里找到更多：https: //stackoverflow.com/a/24777235/4120319
Here's the full SQL:
这是完整的 SQL：
SET sql_mode='PIPES_AS_CONCAT';
SELECT * FROM tableOne
LEFT JOIN tableTwo
ON tableTwo.query = 'category_id=' || tableOne.category_id;
