MySQL FIND_IN_SET函数的使用场景

FIND_IN_SET(str, strlist)

-- 创建测试表
CREATE TABLE articles (
    id INT PRIMARY KEY,
    title VARCHAR(100),
    tags VARCHAR(200)
);

-- 插入测试数据
INSERT INTO articles VALUES
(1, '深入理解MySQL', 'mysql,database,tech'),
(2, 'Python入门教程', 'python,programming,beginner'),
(3, '前端开发实践', 'javascript,html,css');

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

-- 查找包含多个标签之一的文章
SELECT * FROM articles 
WHERE FIND_IN_SET('mysql', tags) > 0 
   OR FIND_IN_SET('python', tags) > 0;

-- 结合 CASE 使用
SELECT 
    title,
    CASE 
        WHEN FIND_IN_SET('tech', tags) > 0 THEN '技术类'
        WHEN FIND_IN_SET('beginner', tags) > 0 THEN '入门类'
        ELSE '其他'
    END AS category
FROM articles;

-- 结合 COUNT 统计
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;

-- 创建存储过程实现动态标签搜索
DELIMITER //
CREATE PROCEDURE search_by_tags(IN tag_list VARCHAR(1000))
BEGIN
    SET @sql = 'SELECT * FROM articles WHERE 1=1';
    
    -- 分割输入的标签
    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');
        
        -- 移除已处理的标签
        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 ;

-- 调用存储过程
CALL search_by_tags('mysql,tech');

-- 使用 LOWER 或 UPPER 函数处理大小写
SELECT * FROM articles 
WHERE FIND_IN_SET(LOWER('MySQL'), LOWER(tags)) > 0;

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

-- 结合 LIKE 实现模糊匹配
SELECT * FROM articles 
WHERE tags LIKE CONCAT('%', 'mysql', '%')
   OR FIND_IN_SET('mysql', tags) > 0;