what is mysql ft-Mysql Tutorial-php.cn

mysql ft refers to FullText, that is, full-text index; full-text index is to solve queries that need to be based on similarity, rather than precise numerical comparison; full-text index can be N times faster than like in the face of a large amount of data. Speed is not an order of magnitude.

what is mysql ft

The operating environment of this tutorial: Windows 10 system, mysql8 version, Dell G3 computer.

What is mysql ft?

That is, full-text index (FullText).

MySQL full-text index (FullText)

1. Introduction

Basic concepts

Full-text index is to solve the need to be based on similarity queries rather than exact numerical comparisons.

Although fuzzy matching can also be achieved using like %, it is unimaginable for retrieval of large amounts of text data. In the face of a large amount of data, full-text indexing can be N times faster than like, but the speed is not an order of magnitude.

Version support

MySQL 5.6 In previous versions, only MyISAM storage engine supports full-text index
MySQL 5.6 and later versions, MyISAM and InnoDB storage engines support full-text index
MySQL 5.7.6, Provides a built-in full-text ngram parser that supports Chinese, Japanese, and Korean (CJK), as well as an installable MeCab full-text parser plug-in for Japanese
Full-text index Can only be used for InnoDB or MyISAM tables, and can only be created# for CHAR, VARCHAR, TEXT columns

Load the data into a database without full-text indexing Then creating an index in the table is much faster than loading data into a table with an existing full-text index

RDS MySQL 5.6 Although Chinese full-text retrieval is also supported, there are BUG

Limitations and Disadvantages

Results in a large occupation of disk resources. Full-text indexing itself is a method of using disk space for performance. The reason why the full-text index is large is that word segmentation is performed according to a certain language
Using the full-text index is not Transparent to the application. If you want to use the full-text index, you must modify the query statement. It is impossible to use the full-text index for the original query statement, and needs to be changed to the syntax specified by the full-text index
Not case sensitive
Partitioned tables do not support full-text search
By The index of the full-text search composed of multiple columns must use the same character set and sorting rules
Full-text index may have accuracy issues, that is, the data found by the full-text index may not be the same as likeInconsistency
When the full-text index is established separately for a single column, the multi-column fuzzy query does not take effect
The full-text indexes of different tables cannot be queried together. They can be queried in two Add OR

to each statement. 2. Operate the full-text index

2.1 Configure the minimum search length

We can view the currently configured minimum search length through SQL commands ( Word segment length):

SHOW VARIABLES LIKE 'ft%';

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##Variable_name##ft_boolean_syntax -><()~*:""&|ft_max_word_len84120(built-in )

Value

##ft_min_word_len

ft_query_expansion_limit

ft_stopword_file

全文索引的相关参数都无法进行动态修改，必须通过修改 MySQL 的配置文件来完成。修改最小搜索长度的值为 1，首先打开 MySQL 的配置文件 /etc/my.cnf，在 [mysqld] 的下面追加以下内容：

[mysqld]
innodb_ft_min_token_size = 1
# 最短的索引字符串，默认值为4
ft_min_word_len = 1

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配置完后重启 MySQL 服务器，并修复或重建全文索引方可生效。
可使用下面的命令修复：

repair table test quick;

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2.2 创建索引

建表时创建全文索引

CREATE TABLE fulltext_test (
  id int(11) NOT NULL AUTO_INCREMENT,
	content TEXT NOT NULL,
	tag VARCHAR(255),
	PRIMARY KEY (id),
	FULLTEXT KEY content_tag_fulltext(content, tag) WITH PARSER ngram
) ENGINE = InnoDB DEFAULT CHARSET=utf8mb4;

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在已存在的表上创建全文索引

CREATE FULLTEXT INDEX content_fulltext ON fulltext_test(content) with parser ngram;

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通过 SQL 语句 ALTER TABLE 创建全文索引

ALTER TABLE fulltext_test ADD FULLTEXT INDEX content_fulltext(content) with parser ngram;

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2.3 删除索引

使用 DROP INDEX 删除全文索引

DROP INDEX content_fulltext ON fulltext_test;

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通过 SQL 语句 ALTER TABLE 删除全文索引

ALTER TABLE fulltext_test DROP INDEX content_fulltext;

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三、检索数据

3.1 自然语言的全文检索

默认情况下，或者使用 in natural language mode 修饰符时，match() 函数对文本集合执行自然语言搜索。

SELECT * FROM 表名 WHERE Match(列名1,列名2) Against (检索内容1 检索内容2);

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检索内容不需要用逗号隔开！

自然语言搜索引擎将计算每一个文档对象和查询的相关度。这里，相关度是基于匹配的关键词的个数，以及关键词在文档中出现的次数。在整个索引中出现次数越少的词语，匹配时的相关度就越高。相反，非常常见的单词将不会被搜索，如果一个词语的在超过 50% 的记录中都出现了，那么自然语言的搜索将不会搜索这类词语。

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3.2 布尔全文检索

在布尔搜索中，我们可以在查询中自定义某个被搜索的词语的相关性，当编写一个布尔搜索查询时，可以通过一些前缀修饰符来定制搜索。

空(也就是默认状况)，表示可选的，包含该词的顺序较高
+ 表示必须包含
- 表示必须排除
“>” 表示出现该单词时增加相关性，查询的结果靠前
“<” 表示出现该单词时降低相关性，查询的结果靠后
* 表示通配符，只能接在词后面
~ 允许出现该单词，但是出现时相关性为负，表示拥有该字会下降相关性，但不像「-」将之排除，只是排在较后面
"" 双引号表示短语，表示要彻底相符，不可拆字效果，类同于 like '%keyword%'
() 经过括号来使用字条件:

+aaa +(>bbb <ccc) aaa="aaa" sql="sql" select="select" from="from" test="test" where="where" match="match" against="against" in="in" boolean="boolean" mode="mode" select="select" from="from" tommy="tommy" where="where" match="match" against="against" in="in" boolean="boolean" mode="mode" select="select" from="from" tommy="tommy" where="where" match="match" against="against">李秀琴 <练习册 <不是人>是个鬼' in boolean mode);<h2 id="四-测试结果">四、测试结果</h2>
<p><strong>测试环境</strong>：本机4核16G Windows10，MySQL 8.0<br><strong>测试数据量</strong>：<code>salebilldetail</code> 表 <code>1276</code>万行，<code>salebill</code> 表 <code>269</code> 万行, <code>customer</code> 表 <code>30</code> 万行, <code>goods</code> 表 <code>75</code> 万行。</p>
<p>争对测试用的SQL语句，增加了以下全文索引：</p>
<pre class="brush:php;toolbar:false">CREATE FULLTEXT INDEX billno_fulltext ON salebill(billno) WITH PARSER ngram;
CREATE FULLTEXT INDEX remarks_fulltext ON salebill(remarks) WITH PARSER ngram;
CREATE FULLTEXT INDEX remarks_fulltext ON salebilldetail(remarks) WITH PARSER ngram;
CREATE FULLTEXT INDEX goodsremarks_fulltext ON salebilldetail(goodsremarks) WITH PARSER ngram;
CREATE FULLTEXT INDEX remarks_goodsremarks_fulltext ON salebilldetail(remarks, goodsremarks) WITH PARSER ngram;
CREATE FULLTEXT INDEX custname_fulltext ON customer(custname) WITH PARSER ngram;
CREATE FULLTEXT INDEX goodsname_fulltext ON goods(goodsname) WITH PARSER ngram;
CREATE FULLTEXT INDEX goodscode_fulltext ON goods(goodscode) WITH PARSER ngram;

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测试结果，总的来说很魔幻。
为什么魔幻，看下面几个语句：

test_1

-- 测试1，原始 like 查询方式，用时 0.765s
select 1 from salebilldetail d where d.tid=260434 and ((d.remarks like concat('%','葡萄','%')) or (d.goodsremarks like concat('%','葡萄','%')));

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test_2

-- 测试2，使用全文索引 remarks_fulltext、goodsremarks_fulltext, 用时 0.834s
select 1 from salebilldetail d where d.tid=260434 and ((match(d.remarks) Against(concat('"','葡萄','"') in boolean mode)) or (match(d.goodsremarks) Against(concat('"','葡萄','"')  in boolean mode)));

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test_3

-- 测试3，使用全文索引 remarks_goodsremarks_fulltext, 用时 0.242s
select 1 from salebilldetail d where d.tid=260434 and ((match(d.remarks,d.goodsremarks) Against(concat('"','葡萄','"') in boolean mode)));

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test_4

-- 测试4，原始 like 查询方式，不过滤 tid ，用时 22.654s
select t from salebilldetail d where ((d.remarks like concat('%','葡萄','%')) or (d.goodsremarks like concat('%','葡萄','%')));

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test_5

-- 测试5，使用全文索引 remarks_fulltext、goodsremarks_fulltext,  不过滤 tid ，用时 24.855s
select 1 from salebilldetail d where ((match(d.remarks) Against(concat('"','葡萄','"') in boolean mode)) or (match(d.goodsremarks) Against(concat('"','葡萄','"')  in boolean mode)));

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test_6

-- 测试6，使用全文索引 remarks_goodsremarks_fulltext, 不过滤 tid ，用时 0.213s
select 1 from salebilldetail d where ((match(d.remarks,d.goodsremarks) Against(concat('"','葡萄','"') in boolean mode)));

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test_7

-- 测试7，使用全文索引 remarks_goodsremarks_fulltext, 用时 0.22s
select count(1) from salebilldetail d where d.tid=260434 and  ((match(d.remarks,d.goodsremarks) Against(concat('"','葡萄','"') in boolean mode)));

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test_8

-- 测试8，使用全文索引 remarks_goodsremarks_fulltext, 不过滤 tid ，用时 0.007s
select count(1) from salebilldetail d where ((match(d.remarks,d.goodsremarks) Against(concat('"','葡萄','"') in boolean mode)));

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从上面的测试语句可以看出，数据量越多，查询越简单，全文索引的效果越好。

再来看看我们的业务测试SQL:

test_9

-- 测试9
select 
    i.billid
    ,if(0,0,i.qty) as qty  
    ,if(0,0,i.goodstotal) as total          
    ,if(0,0,i.chktotal) as selfchktotal   
    ,if(0,0,i.distotal) as distotal 
    ,if(0,0,i.otherpay) as feetotal  
    ,if(0,0,ifnull(d.costtotal,0)) as costtotal  
    ,if(0,0,ifnull(d.maoli,0)) as maoli         
    ,i.billno
    ,from_unixtime(i.billdate,'%Y-%m-%d') as billdate /*单据日期*/
    ,from_unixtime(i.createdate,'%Y-%m-%d %H:%i:%s') as createdate /*制单日期*/
    ,if(i.sdate=0,'',from_unixtime(i.sdate,'%Y-%m-%d  %H:%i:%s')) as sdate /*过账日期*/
    ,from_unixtime(i.udate,'%Y-%m-%d %H:%i:%s') as udate /*最后修改时间*/
    ,i.custid ,c.custname
    ,i.storeid ,k.storename
    ,i.empid ,e.empname
    ,i.userid ,u.username
    ,i.remarks                               /*单据备注*/
    ,i.effect,i.settle,i.redold,i.rednew     /*单据状态*/
    ,i.printtimes /* 打印次数 */
    ,(case  when i.rednew=1 then 1  when i.redold=1 then 2  when i.settle=1 then 3  when i.effect=1 then 4  else 9 end) as state /*单据状态*/
    ,(case  when i.rednew=1 then '红冲单'  when i.redold=1 then '已红冲'  when i.settle=1 then '已结算'  when i.effect=1 then '已过账'  else '草稿' end) as statetext
    ,'' as susername /* 操作人 */
    ,'' as accname /* 科目 */
from salebill i
left join coursecentersale d on d.tid=i.tid and d.billid=i.billid
left join customer c on c.tid=i.tid and c.custid=i.custid
left join store k on k.tid=i.tid and k.storeid=i.storeid
left join employee e on e.tid=i.tid and e.empid=i.empid
left join user u on u.tid=i.tid and u.userid=i.userid
where i.tid=260434 and (i.billtype = 5 or i.effect = 1)
    and ('_billdate_f_'!='')
    and ('_billdate_t_'!='')
    and ('_sdate_f_'!='')
    and ('_sdate_t_'!='')
    and ('_udate_f_'!='')
    and ('_udate_t_'!='')
    and ('_cdate_f_'!='')
    and ('_cdate_t_'!='')
    and ('_billid_'!='')      /*单据id*/
    and ('_custid_'!='')      /*客户ID*/
    and ('_storeid_'!='')     /*店仓ID*/
    and ('_empid_'!='')       /*业务员ID*/
    and ('_custstop_'!='')       /*客户是否停用*/
    and (
        (i.billno like concat('%','葡萄','%'))
        or (i.remarks like concat('%','葡萄','%'))
        or exists(select 1 from salebilldetail d where d.tid=260434 and d.billid=i.billid and ((d.remarks like concat('%','葡萄','%')) or (d.goodsremarks like concat('%','葡萄','%'))))
        or exists(select 1 from customer c where c.tid=260434 and c.custid=i.custid and (c.custname like concat('%','葡萄','%')))
        or exists(select 1 from goods g join salebilldetail d on d.tid=g.tid and d.goodsid=g.goodsid where d.tid=260434 and d.billid=i.billid and ((g.goodsname like concat('%','葡萄','%')) or (g.goodscode like concat('%','葡萄','%'))))
    )
    and i.rednew=0 /*单据列表不含红冲单*/ 
    and i.billid not in (select billid from coursecenter_del t where t.tid=260434)
    and ((i.settle=1 and i.effect=1 and i.redold=0 and i.rednew=0)) /*已结算*/
order by udate desc,billno desc
limit 0,100;

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执行时间约 1.6 秒，使用的是 like 方式。

改成使用全文索引方式：

test_10

-- 测试10
select 
    i.billid
    ,if(0,0,i.qty) as qty         
    ,if(0,0,i.goodstotal) as total   
    ,if(0,0,i.chktotal) as selfchktotal  
    ,if(0,0,i.distotal) as distotal 
    ,if(0,0,i.otherpay) as feetotal  
    ,if(0,0,ifnull(d.costtotal,0)) as costtotal 
    ,if(0,0,ifnull(d.maoli,0)) as maoli  
    ,i.billno
    ,from_unixtime(i.billdate,'%Y-%m-%d') as billdate /*单据日期*/
    ,from_unixtime(i.createdate,'%Y-%m-%d %H:%i:%s') as createdate /*制单日期*/
    ,if(i.sdate=0,'',from_unixtime(i.sdate,'%Y-%m-%d  %H:%i:%s')) as sdate /*过账日期*/
    ,from_unixtime(i.udate,'%Y-%m-%d %H:%i:%s') as udate /*最后修改时间*/
    ,i.custid ,c.custname
    ,i.storeid ,k.storename
    ,i.empid ,e.empname
    ,i.userid ,u.username
    ,i.remarks                               /*单据备注*/
    ,i.effect,i.settle,i.redold,i.rednew     /*单据状态*/
    ,i.printtimes /* 打印次数 */
    ,(case  when i.rednew=1 then 1  when i.redold=1 then 2  when i.settle=1 then 3  when i.effect=1 then 4  else 9 end) as state /*单据状态*/
    ,(case  when i.rednew=1 then '红冲单'  when i.redold=1 then '已红冲'  when i.settle=1 then '已结算'  when i.effect=1 then '已过账'  else '草稿' end) as statetext
    ,'' as susername /* 操作人 */
    ,'' as accname /* 科目 */
from salebill i
left join coursecentersale d on d.tid=i.tid and d.billid=i.billid
left join customer c on c.tid=i.tid and c.custid=i.custid
left join store k on k.tid=i.tid and k.storeid=i.storeid
left join employee e on e.tid=i.tid and e.empid=i.empid
left join user u on u.tid=i.tid and u.userid=i.userid
where i.tid=260434 and (i.billtype = 5 or i.effect = 1)
    and ('_billdate_f_'!='')
    and ('_billdate_t_'!='')
    and ('_sdate_f_'!='')
    and ('_sdate_t_'!='')
    and ('_udate_f_'!='')
    and ('_udate_t_'!='')
    and ('_cdate_f_'!='')
    and ('_cdate_t_'!='')
    and ('_billid_'!='')      /*单据id*/
    and ('_custid_'!='')      /*客户ID*/
    and ('_storeid_'!='')     /*店仓ID*/
    and ('_empid_'!='')       /*业务员ID*/
    and ('_custstop_'!='')       /*客户是否停用*/
    and (
        (match(i.billno) against(concat('"','葡萄','"') in boolean mode))
        or (match(i.remarks) against(concat('"','葡萄','"') in boolean mode))
        or exists(select 1 from salebilldetail d where d.tid=260434 and d.billid=i.billid and ((match(d.remarks) Against(concat('"','葡萄','"') in boolean mode)) or (match(d.goodsremarks) Against(concat('"','葡萄','"')  in boolean mode))))
        or exists(select 1 from customer c where c.tid=260434 and c.custid=i.custid and (match(c.custname) Against(concat('"','葡萄','"') in boolean mode)))
        or exists(select 1 from goods g join salebilldetail d on d.tid=g.tid and d.goodsid=g.goodsid where d.tid=260434 and d.billid=i.billid 
     and ((match(g.goodsname) Against(concat('"','葡萄','"') in boolean mode))
     or (match(g.goodscode) Against(concat('"','葡萄','"') in boolean mode))))
    )
    and i.rednew=0 /*单据列表不含红冲单*/ 
    and i.billid not in (select billid from coursecenter_del t where t.tid=260434)
    and ((i.settle=1 and i.effect=1 and i.redold=0 and i.rednew=0)) /*已结算*/
order by udate desc,billno desc
limit 0,100;

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执行时间约 1.6 秒，与使用的是 like 方式差不多。

最魔幻的地方来了，如果将上面的SQL语句中（salebilldetail表使用全文索引 remarks_fulltext、goodsremarks_fulltext的地方）

exists(select 1 from salebilldetail d where d.tid=260434 and d.billid=i.billid and ((match(d.remarks) Against(concat('"','葡萄','"') in boolean mode)) or (match(d.goodsremarks) Against(concat('"','葡萄','"')  in boolean mode))))

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test_11

改成使用全文索引 remarks_goodsremarks_fulltext

-- 测试11
exists(select 1 from salebilldetail d where d.tid=260434 and d.billid=i.billid and ((match(d.remarks,d.goodsremarks) Against(concat('"','葡萄','"') in boolean mode))))

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执行时间无限长（跑了半天没成功）？
经分析，在 where 子句中，一个条件子句中包含一个以上 match 时会出现这样的情况。即：

-- and 中只有一个全文检索时正常， 用时0.2秒
select xxx from xxx
...
and (
	exists(select 1 from salebilldetail d where d.tid=260434 and d.billid=i.billid and ((match(d.remarks,d.goodsremarks) Against(concat('"','葡萄','"') in boolean mode))))
)
...

-- 下面这样就异常了，会慢成百上千倍，用时 160 秒， 如果有更多的 match ，会更夸张的慢下去
select xxx from xxx
...
and (
	exists(select 1 from salebilldetail d where d.tid=260434 and d.billid=i.billid and ((match(d.remarks,d.goodsremarks) Against(concat('"','葡萄','"') in boolean mode))))
	or match(i.billno) against(concat('"','葡萄','"') in boolean mode)
)
...

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测试结果汇总：

查询	用时(秒)	备注
test 1	0.765	原始`like`查询
test 2	0.834	全文索引 `remarks_fulltext`、`goodsremarks_fulltext`
test 3	0.242	全文索引 `remarks_goodsremarks_fulltext`
---
test 4	22.654	原始`like`查询，不过滤 tid
test 5	24.855	全文索引 `remarks_fulltext`、`goodsremarks_fulltext`, 不过滤 tid
test 6	0.213	全文索引 `remarks_goodsremarks_fulltext`, 不过滤 tid
---
test 7	0.22	全文索引 `remarks_goodsremarks_fulltext`, count
test 8	0.007	全文索引 `remarks_goodsremarks_fulltext`, 不过滤 tid, count
---
test 9	1.6	业务测试SQL，原始`like`查询
test 10	1.6	业务测试SQL，全文索引 `remarks_fulltext`、`goodsremarks_fulltext`
test 11	失败	业务测试SQL，全文索引 `remarks_goodsremarks_fulltext`

五、MySQL 版本升级

因线上系统目前是 RDS MySQL 5.6，故简单描述升级相关问题。

Group By: 在 MySQL 5.7 之后，默认使用增加了限制，一些在 MySQL 5.6 可执行的Group By语句，在 5.7 之后会报错，可以更改新版本 MySQL 的 sqlModel
- 方式1：重启 MySQL 后失效
```
-- 查询 sql_mode
select @@SESSION.sql_mode;
-- 设置
SET GLOBAL sql_mode = 'STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION';
-- 或 设置 （修改于当前会 话，关闭当前会话后失效）
SET SESSION sql_mode = 'STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION';
-- 刷新
flush PRIVILEGES;
```
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- 方式2：在配置文件中添加 sql_mode = '对应需要的模式'
- sql_mode 模式说明：
  - ONLY_FULL_GROUP_BY: 对于GROUP BY聚合操作，如果在SELECT中的列，没有在GROUP BY中出现，那么这个SQL是不合法的，因为列不在GROUP BY从句中
  - NO_AUTO_VALUE_ON_ZERO: 该值影响自增长列的插入。默认设置下，插入0或NULL代表生成下一个自增长值。如果用户希望插入的值为0，而该列又是自增长的，那么这个选项就有用了。
  - STRICT_TRANS_TABLES：在该模式下，如果一个值不能插入到一个事务中，则中断当前的操作，对非事务表不做限制
  - NO_ZERO_IN_DATE：在严格模式下，不允许日期和月份为零
  - NO_ZERO_DATE：设置该值，mysql数据库不允许插入零日期，插入零日期会抛出错误而不是警告
  - ERROR_FOR_DIVISION_BY_ZERO：在insert或update过程中，如果数据被零除，则产生错误而非警告。如果未给出该模式，那么数据被零除时MySql返回NULL
  - NO_AUTO_CREATE_USER: 禁止GRANT创建密码为空的用户
  - NO_ENGINE_SUBSTITUTION：如果需要的存储引擎被禁用或未编译，那么抛出错误。不设置此值时，用默认的存储引擎替代，并抛出一个异常
  - PIPES_AS_CONCAT：将"||"视为字符串的连接操作符而非或运算符，这和Oracle数据库是一样是，也和字符串的拼接函数Concat想类似
  - ANSI_QUOTES：启用后，不能用双引号来引用字符串，因为它被解释为识别符
MySQL8.0 修改了账号密码加密策略 (默认的认证插件由mysql_native_password更改为caching_sha2_password），导致一些可视化软件无法连接 mysql8.0 版本的数据库。如果需要，可以修改默认的策略或者账号密码的认证策略
- 方式1：配置文件中添加, 让mysql使用原密码策略 (需重启mysql服务)
```
[mysqld]
default_authentication_plugin = mysql_native_password
```
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- 方式2：执行语句修改某账号密码验证策略
```
-- 修改加密规则 
ALTER USER 'root'@'localhost' IDENTIFIED BY 'password' PASSWORD EXPIRE NEVER; 
-- 更新用户密码
ALTER USER '账号'@'%' IDENTIFIED WITH mysql_native_password BY '密码';
-- 刷新权限
FLUSH PRIVILEGES;
```
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MySQL8.0 授权用户账号语法变更，创建用户的操作已经不支持grant的同时创建用户方式，需要先创建用户再进行授权。

-- 原来的流程：
mysql> grant all on *.* to 'admin'@'%' identified by 'admin';
-- 新的正确流程：
mysql> create user 'admin'@'%' identified by 'admin';
mysql> grant all on *.* to 'admin'@'%' ;
mysql> flush privileges;

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数据库连接区别

JDBC 连接串修改如下（首先需要驱动使用8.0对应连接的驱动）：

jdbc:mysql://{ip}:{port}/{db}&#63;characterEncoding=utf8&useSSL=false&serverTimezone=UTC
// useSSL  如果不配置false 项目可以正常启动但是会提示ssl问题
// serverTimezone=UTC 必须配置【时区设置成自己对应的时区】否则项目会报错

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如果时区问题还不能解决：

show variables like '%time_zone%'；
set global time_zone='+8:00';

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MySQL 5.7 原生支持JSON类型，并引入了众多JSON函数
MySQL 8.0 JSON字段的部分更新（JSON Partial Updates）
MySQL 8.0 默认字符集由latin1修改为utf8mb4
MySQL 8.0 正则表达式的增强，新增了4个相关函数，REGEXP_INSTR()，REGEXP_LIKE()，REGEXP_REPLACE()，REGEXP_SUBSTR()
MySQL 8.0 GROUP BY语句不再隐式排序（忽略在Group By中的排序命令，如 desc, asc）

【相关推荐：mysql视频教程】

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