mariadb mysql 语法_Mariadb MySQL、Mariadb中GROUP_CONCAT函数使用介绍
MySQL、Mariadb中GROUP_CONCAT 函數使用介紹
By:授客 QQ：1033553122
語法：
GROUP_CONCAT([DISTINCT] column_name [ORDER BY 序字段 ASC/DESC] [SEPARATOR '分隔符'])
注：測試時發現，排序似乎不起作用
實踐
構造數據：
CREATE TABLE tb_test(
order_id INT,
goods_id INT,
user_name VARCHAR(7)
);
INSERT INTO tb_test VALUES(1000000001, 1, '授客'), (1000000001, 2, '授客'), (1000000001, 3, '授客'),(1000000002, 4, '小謝'), (1000000002, 5, '小謝'), (1000000002, 6, '小謝');
SELECT * FROM tb_test;
例子1：
查詢每個用戶購買的商品(按user_name分組，顯示其購買的所有商品)
SELECT t1.`order_id` AS '訂單號',
t1.`user_name` AS '用戶名',
GROUP_CONCAT((CASE WHEN t1.`goods_id` = 1 THEN '小蘋果'
WHEN t1.`goods_id` = 2 THEN '雪梨'
WHEN t1.`goods_id` = 3 THEN '香蕉'
WHEN t1.`goods_id` = 4 THEN '小李子'
WHEN t1.`goods_id` = 5 THEN '芭樂'
WHEN t1.`goods_id` = 6 THEN '葡萄'
END)) AS '商品'
FROM tb_test t1
GROUP BY t1.`user_name`;
結果：
例子2：
查詢每個用戶購買的商品(按user_name分組，顯示其購買的所有商品)，商品之間用";"分隔
SELECT t1.`order_id` AS '訂單號',
t1.`user_name` AS '用戶名',
GROUP_CONCAT((CASE WHEN t1.`goods_id` = 1 THEN '小蘋果'
WHEN t1.`goods_id` = 2 THEN '雪梨'
WHEN t1.`goods_id` = 3 THEN '香蕉'
WHEN t1.`goods_id` = 4 THEN '小李子'
WHEN t1.`goods_id` = 5 THEN '芭樂'
WHEN t1.`goods_id` = 6 THEN '葡萄'
END) SEPARATOR ';') AS '商品'
FROM tb_test t1
GROUP BY t1.`user_name`;
結果：
例子3：
查詢每個用戶購買的商品(按user_name分組，顯示其購買的所有商品)，商品名稱不重復
SELECT t1.`order_id` AS '訂單號',
t1.`user_name` AS '用戶名',
GROUP_CONCAT((CASE WHEN t1.`goods_id` = 1 THEN '小蘋果'
WHEN t1.`goods_id` = 2 THEN '雪梨'
WHEN t1.`goods_id` = 3 THEN '香蕉'
WHEN t1.`goods_id` = 4 THEN '小李子'
WHEN t1.`goods_id` = 5 THEN '芭樂'
WHEN t1.`goods_id` = 6 THEN '葡萄'
END) ) AS '商品'
FROM tb_test t1
GROUP BY t1.`user_name`;
運行結果：
修改腳本如下：
SELECT t1.`order_id` AS '訂單號',
t1.`user_name` AS '用戶名',
GROUP_CONCAT(DISTINCT (CASE WHEN t1.`goods_id` = 1 THEN
'小蘋果'
WHEN t1.`goods_id` = 2 THEN '雪梨'
WHEN t1.`goods_id` = 3 THEN '香蕉'
WHEN t1.`goods_id` = 4 THEN '小李子'
WHEN t1.`goods_id` = 5 THEN '芭樂'
WHEN t1.`goods_id` = 6 THEN '葡萄'
END) ) AS '商品'
FROM tb_test t1
GROUP BY t1.`user_name`;
運行結果如下：
總結
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