Concatenate string with field value in MySQL [duplicate]

Answer 1

SELECT ..., CONCAT( 'category_id=', tableOne.category_id) as query2  FROM tableOne 
LEFT JOIN tableTwo
ON tableTwo.query = query2

Answer 2

Have you tried using the concat() function?

ON tableTwo.query = concat('category_id=',tableOne.category_id)

Answer 3

MySQL uses CONCAT() to concatenate strings

SELECT * FROM tableOne 
LEFT JOIN tableTwo
ON tableTwo.query = CONCAT('category_id=', tableOne.category_id)

Answer 4

Here is a great answer to that:

SET sql_mode='PIPES_AS_CONCAT';

Find more here: https://stackoverflow.com/a/24777235/4120319

Here's the full SQL:

SET sql_mode='PIPES_AS_CONCAT';

SELECT * FROM tableOne 
LEFT JOIN tableTwo
ON tableTwo.query = 'category_id=' || tableOne.category_id;