写sql对于php来说是经常的事，那么如何对sql语句进行分析来优化sql呢？sql-parser就提供了这样的功能，让我们一起来看看吧。
phpMyAdmin是一款基于Web端运行的开源数据库管理工具，支持管理MySQL和MariaDB两种数据库。 phpMyAdmin的程序主要使用php和javascript开发，它的安装使用都比较简单而且已有很多相关介绍不再重复，今天要介绍的是源码中的一个核心组件sql-parser。
sql-parser简介
sql-parser组件的主要用途是对SQL语句进行词法分析、语法分析，继而可以实现对SQL语句的解构、加工、替换、再组装等需求，另外也可以对SQL进行highlight等处理。sql-parser由纯PHP语言实现，同时也是整个phpMyAdmin源码中为数不多的代码架构比较清晰且符合当前PHP界PSR标准规范的模块。
sql-parser组件安装
需事先安装好php，git客户端，以及composer php包管理工具
margin@margin-MB1:~/tmp$ sudo git clone https://github.com/phpmyadmin/sql-parser.git margin@margin-MB1:~/tmp$ cd sql-parser && sudo composer install
组件安装完毕，下面介绍具体的调用
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解析普通语句
require_once '../sql-parser/vendor/autoload.php';
use SqlParser\Parser;
$query = 'SELECT * FROM t1 LEFT JOIN (t2, t3, t4) '
. 'ON (t2.a=t1.a AND t3.b=t1.b AND t4.c=t1.c)';
$parser = new Parser($query);
$stmt = $parser->statements[0];
echo json_encode($stmt);运行结果中$parser变量是一个大对象，里面存储有对$query语句的词法分析结果$query->list，语法分析结果$query-statements，以及错误信息等。
其中$query-statements的结构如下：
{"expr":
[{"database":null,"table":null,"column":null,"expr":"*","alias":null,"function":n
ull,"subquery":null}],"from":
[{"database":null,"table":"t1","column":null,"expr":"t1","alias":null,"function":
null,"subquery":null}],"partition":null,"where":null,"group":null,"having":null,"
order":null,"limit":null,"procedure":null,"into":null,"join":
[{"type":"LEFT","expr":{"database":null,"table":null,"column":null,"expr":"(t2,
t3, t4)","alias":null,"function":null,"subquery":null},"on":[{"identifiers":
["t2","a","t1"],"isOperator":false,"expr":"(t2.a=t1.a"},{"identifiers":
[],"isOperator":true,"expr":"AND"},{"identifiers":
["t3","b","t1"],"isOperator":false,"expr":"t3.b=t1.b"},{"identifiers":
[],"isOperator":true,"expr":"AND"},{"identifiers":
["t4","c","t1"],"isOperator":false,"expr":"t4.c=t1.c)"}],"using":null}],"union":
[],"options":{"options":[]},"first":0,"last":50}
解析事务
require_once '../sql-parser/vendor/autoload.php';
use SqlParser\Parser;
$query = 'START TRANSACTION;' .
'SELECT @A:=SUM(salary) FROM table1 WHERE type=1;' .
'UPDATE table2 SET summary=@A WHERE type=1;' .
'COMMIT;';
$parser = new Parser($query);
$stmt = $parser->statements[0];
echo json_encode($stmt);输出结果：
{"type":1,"statements":[{"expr":
[{"database":null,"table":null,"column":null,"expr":"@A:=SUM(salary)","alias":nul
l,"function":"SUM","subquery":null}],"from":
[{"database":null,"table":"table1","column":null,"expr":"table1","alias":null,"fu
nction":null,"subquery":null}],"partition":null,"where":[{"identifiers":
["type"],"isOperator":false,"expr":"type=1"}],"group":null,"having":null,"order":
null,"limit":null,"procedure":null,"into":null,"join":null,"union":[],"options":
{"options":[]},"first":1,"last":19},{"tables":
[{"database":null,"table":"table2","column":null,"expr":"table2","alias":null,"fu
nction":null,"subquery":null}],"set":[{"column":"summary","value":"@A"}],"where":
[{"identifiers":
["type"],"isOperator":false,"expr":"type=1"}],"order":null,"limit":null,"options"
:{"options":[]},"first":20,"last":35}],"end":
{"type":2,"statements":null,"end":null,"options":{"options":
{"1":"COMMIT"}},"first":36,"last":37},"options":{"options":{"1":"START
TRANSACTION"}},"first":0,"last":0}除以上两种语句之外，sql-parser还支持解析存储过程等几乎所有MySQL语法，不再一一举例。下面是其SQL构造器的用法举例。
组装SQL语句
组装select语句：
require_once '../sql-parser/vendor/autoload.php';
use SqlParser\Components\OptionsArray;
use SqlParser\Components\Expression;
use SqlParser\Components\Condition;
use SqlParser\Components\Limit;
use SqlParser\Statements\SelectStatement;
$stmt = new SelectStatement();
$stmt->options = new OptionsArray(array('DISTINCT'));
$stmt->expr[] = new Expression('sakila', 'film', 'film_id', 'fid');
$stmt->expr[] = new Expression('COUNT(film_id)');
$stmt->from[] = new Expression('', 'film', '');
$stmt->from[] = new Expression('', 'actor', '');
$stmt->where[] = new Condition('film_id > 10');
$stmt->where[] = new Condition('OR');
$stmt->where[] = new Condition('actor.age > 25');
$stmt->limit = new Limit(1, 10);
var_dump($stmt->build());输出结果：
margin@margin-MB1:~/code/parserTest$ php build.php string(137) "SELECT DISTINCT `sakila`.`film`.`film_id` AS `fid`, COUNT(film_id) FROM `film`, `actor` WHERE film_id > 10 OR actor.age > 25 LIMIT 10, 1 "
组装触发器语句：
require_once '../sql-parser/vendor/autoload.php';
use SqlParser\Components\Expression;
use SqlParser\Components\OptionsArray;
use SqlParser\Statements\CreateStatement;
$stmt = new CreateStatement();
$stmt->options = new OptionsArray(array('TRIGGER'));
$stmt->name = new Expression('ins_sum');
$stmt->entityOptions = new OptionsArray(array('BEFORE', 'INSERT'));
$stmt->table = new Expression('account');
$stmt->body = 'SET @sum = @sum + NEW.amount';
var_dump($stmt->build());
输出结果：
margin@margin-MB1:~/code/parserTest$ php build.php string(89) "CREATE TRIGGER ins_sum BEFORE INSERT ON account FOR EACH ROW SET @sum = @sum + NEW.amount"
SQL再加工
多条语句一起加工处理：
require_once '../sql-parser/vendor/autoload.php';
use SqlParser\Parser;
use SqlParser\Components\Expression;
$query = <<<str id="3" from="" change="" $statement_0="$parser-" 处理第一条语句="" parser($query);="" $parser="new" str;="" where="" tbl3="" *="" select="" null;="" not="" unsigned="" )="" 10="" int(="" `field_2`="" `field_1`="" `tbl`="" table="" alter="" auto_increment;="" null="" `uid`="">statements[0];
$statement_0->table = new Expression(
'db2', 'tb2', ''
);
var_dump($statement_0->build());
//处理第二条语句
$statement_1 = $parser->statements[1];
$statement_1->table = new Expression(
'db3', 'tb3', ''
);
var_dump($statement_1->build());</str>输出结果：
margin@margin-MB1:~/code/parserTest$ php build.php string(85) "ALTER TABLE `db2`.`tb2` CHANGE `uid` `uid` INT( 10 ) UNSIGNED NOT NULL AUTO_INCREMENT" string(78) "ALTER TABLE `db3`.`tb3` CHANGE `field_1` `field_2` INT( 10 ) UNSIGNED NOT NULL"
以上是sql-parser组件一些基本的用法示例，phpMyAdmin的sql-parser组件功能比较丰富和完备，本文限了篇幅不能详尽，有兴趣的读者可以通过阅读源码来了解更多高级的用法。
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