MySQL銜接函數concat與group_concat區別

一、group_concat 區別

SELECT
	z_test_demo.id,
	z_test_demo.NAME,
	z_test_demo.age,
	group_concat( z_test_demo2.NAME) 
FROM
	z_test_demo
	LEFT JOIN z_test_demo2 ON z_test_demo.id = z_test_demo2.demo_id
	GROUP BY z_test_demo.id

 

二、concat區別

SELECT
	z_test_demo.id,
	z_test_demo.NAME,
	z_test_demo.age,
	concat(z_test_demo2.id,',',z_test_demo2.NAME) 
FROM
	z_test_demo
	LEFT JOIN z_test_demo2 ON z_test_demo.id = z_test_demo2.demo_id
	GROUP BY z_test_demo.id