FIND_IN_SET(str, strlist)

-- 創(chuàng)建測(cè)試表
CREATE TABLE articles (
    id INT PRIMARY KEY,
    title VARCHAR(100),
    tags VARCHAR(200)
);

-- 插入測(cè)試數(shù)據(jù)
INSERT INTO articles VALUES
(1, '深入理解MySQL', 'mysql,database,tech'),
(2, 'Python入門(mén)教程', 'python,programming,beginner'),
(3, '前端開(kāi)發(fā)實(shí)踐', 'javascript,html,css');

-- 查找包含 'mysql' 標(biāo)簽的文章
SELECT * FROM articles 
WHERE FIND_IN_SET('mysql', tags) > 0;

-- 查找包含多個(gè)標(biāo)簽之一的文章
SELECT * FROM articles 
WHERE FIND_IN_SET('mysql', tags) > 0 
   OR FIND_IN_SET('python', tags) > 0;

-- 結(jié)合 CASE 使用
SELECT 
    title,
    CASE 
        WHEN FIND_IN_SET('tech', tags) > 0 THEN '技術(shù)類(lèi)'
        WHEN FIND_IN_SET('beginner', tags) > 0 THEN '入門(mén)類(lèi)'
        ELSE '其他'
    END AS category
FROM articles;

-- 結(jié)合 COUNT 統(tǒng)計(jì)
SELECT 
    COUNT(*) as article_count,
    SUM(FIND_IN_SET('mysql', tags) > 0) as mysql_count,
    SUM(FIND_IN_SET('python', tags) > 0) as python_count
FROM articles;

-- 創(chuàng)建存儲(chǔ)過(guò)程實(shí)現(xiàn)動(dòng)態(tài)標(biāo)簽搜索
DELIMITER //
CREATE PROCEDURE search_by_tags(IN tag_list VARCHAR(1000))
BEGIN
    SET @sql = 'SELECT * FROM articles WHERE 1=1';
    
    -- 分割輸入的標(biāo)簽
    SET @tags = tag_list;
    WHILE LENGTH(@tags) > 0 DO
        SET @tag = SUBSTRING_INDEX(@tags, ',', 1);
        SET @sql = CONCAT(@sql, 
            ' AND FIND_IN_SET(\'', @tag, '\', tags) > 0');
        
        -- 移除已處理的標(biāo)簽
        IF LOCATE(',', @tags) > 0 THEN
            SET @tags = SUBSTRING(@tags, LOCATE(',', @tags) + 1);
        ELSE
            SET @tags = '';
        END IF;
    END WHILE;
    
    PREPARE stmt FROM @sql;
    EXECUTE stmt;
    DEALLOCATE PREPARE stmt;
END //
DELIMITER ;

-- 調(diào)用存儲(chǔ)過(guò)程
CALL search_by_tags('mysql,tech');

-- 使用 LOWER 或 UPPER 函數(shù)處理大小寫(xiě)
SELECT * FROM articles 
WHERE FIND_IN_SET(LOWER('MySQL'), LOWER(tags)) > 0;

-- 處理 NULL 值和空字符串
SELECT * FROM articles 
WHERE tags IS NOT NULL 
  AND tags != ''
  AND FIND_IN_SET('mysql', tags) > 0;

-- 結(jié)合 LIKE 實(shí)現(xiàn)模糊匹配
SELECT * FROM articles 
WHERE tags LIKE CONCAT('%', 'mysql', '%')
   OR FIND_IN_SET('mysql', tags) > 0;