模糊查询（LIKE） CONCAT(字符串连接函数)

1. 如果需要找出u_name中既有“三”又有“猫”的记录，请使用and条件
   SELECT * FROM [user] WHERE u_name LIKE ‘%三%’ AND u_name LIKE ‘%猫%’

若使用 SELECT * FROM [user] WHERE u_name LIKE ‘%三%猫%’
虽然能搜索出“三脚猫”，但不能搜索出符合条件的“张猫三”。

2.SELECT * FROM [user] WHERE u_name LIKE ‘三’
只找出“唐三藏”这样u_name为三个字且中间一个字是“三”的；

3.SELECT * FROM [user] WHERE u_name LIKE ‘[张李王]三’
将找出“张三”、“李三”、“王三”（而不是“张李王三”）；

4.SELECT * FROM [user] WHERE u_name LIKE ‘[^张李王]三’
将找出不姓“张”、“李”、“王”的“赵三”、“孙三”等；

<select id="findList" resultType="Article">
        SELECT 
            "cmsArticleColumns"/>
        FROM cms_article a
        "cmsArticleJoins"/>
        <where>
            a.del_flag = #{delFlag}
            <if test="title != null and title != ''">
                AND a.title LIKE 
                    <if test="dbName == 'oracle'">'%'||#{title}||'%'if>
                    <if test="dbName == 'mssql'">'%'+#{title}+'%'if>
                    **<if test="dbName == 'mysql'">**CONCAT**('%', #{title}, '%')if>**
            if>
            <if test="posid != null and posid != ''">
                AND a.posid LIKE 
                    <if test="dbName == 'oracle'">'%'||#{posid}||'%'if>
                    <if test="dbName == 'mssql'">'%'+#{posid}+'%'if>
                    <if test="dbName == 'mysql'">CONCAT('%', #{posid}, '%')if>
            if>
            <if test="category.id != null and category.id != ''">
                AND (a.category_id = #{category.id}
                <if test="category.parentIds != null and category.parentIds != ''">
                    or c.parent_ids like 
                        <if test="dbName == 'oracle'">'%'||#{category.id}||'%'if>
                        <if test="dbName == 'mssql'">'%,'+#{category.id}+',%'if>
                        <if test="dbName == 'mysql'">CONCAT('%,', #{category.id}, ',%')if>
                if>)
            if>
            <if test="image != null and image != ''">
                AND a.image  = #{image}
            if>
            <if test="createBy != null and createBy.id != null and createBy.id != ''">
                AND a.create_by  = #{createBy.id}
            if>
            
        where>
        
            "page !=null and page.orderBy != null and page.orderBy != ''">
                ORDER BY ${page.orderBy}
            
            
                ORDER BY a.weight DESC, a.update_date DESC
            
        
    select>

SQL— CONCAT(字符串连接函数)

MySQL: CONCAT()
Oracle: CONCAT(), ||
SQL Server: +
CONCAT() 的语法如下：
CONCAT(字串1, 字串2, 字串3, …): 将字串1、字串2、字串3，等字串连在一起。
请注意，Oracle的CONCAT()只允许两个参数；
换言之，一次只能将两个字串串连起来。不过，在Oracle中，我们可以用’||’来一次串连多个字串。
来看几个例子。假设我们有以下的表格：
Geography 表格
region_name store_name
East Boston
East New York
West Los Angeles
West San Diego
例子1:
MySQL/Oracle:

SELECT CONCAT(region_name,store_name) FROM Geography
WHERE store_name = 'Boston';

结果：
‘EastBoston’
例子2:
Oracle:

SELECT region_name || ' ' || store_name FROM Geography
WHERE store_name = 'Boston';

结果：
‘East Boston’
例子3:
SQL Server:

SELECT region_name + ' ' + store_name FROM Geography
WHERE store_name = 'Boston';

结果：
‘East Boston’