JSqlParser 解析 sql

前言

JSqlParser是一个 SQL 语句解析器。它将 SQL 语句转换为可遍历的 Java 类层次结构，可以方便的用代码对 SQL 语句进行解析，修改等操作。

官网 api 文档和 github 地址如下：

jsqlparser API 文档

jsqlparser github 地址

一、Maven依赖

        
        <dependency>
            <groupId>com.github.jsqlparsergroupId>
            <artifactId>jsqlparserartifactId>
            <version>4.9version>
        dependency>

二、获取sql中的表名

import net.sf.jsqlparser.JSQLParserException;
import net.sf.jsqlparser.util.TablesNamesFinder;
import java.util.Set;

public class MainServer {
    public static void main(String[] args) throws JSQLParserException {
        String sql = "SELECT e.employee_id, e.first_name, e.last_name, d.department_name, e.salary " +
                "FROM employees e " +
                "LEFT JOIN departments d ON e.department_id = d.department_id " +
                "WHERE e.salary > ( " +
                "    SELECT AVG(salary) " +
                "    FROM staff " +
                "    WHERE department_id = e.department_id " +
                ");";
        Set<String> tableNames = TablesNamesFinder.findTables(sql);
		//输出： staff, departments, employees
        System.out.println(tableNames);
    }
}

三、获取sql中的具体信息

import javassist.CannotCompileException;
import net.sf.jsqlparser.JSQLParserException;
import net.sf.jsqlparser.parser.CCJSqlParserUtil;
import net.sf.jsqlparser.statement.Statement;
import net.sf.jsqlparser.statement.select.PlainSelect;
import net.sf.jsqlparser.statement.select.Select;


public class MainServer {
    public static void main(String[] args) throws CannotCompileException, JSQLParserException {
	
        String sql = "SELECT DISTINCT e.employee_id, e.first_name, e.last_name, d.department_name, e.salary " +
                "FROM employees e " +
                "LEFT JOIN departments d ON e.department_id = d.department_id " +
                "WHERE e.salary > ( " +
                "    SELECT AVG(salary) " +
                "    FROM staff " +
                "    WHERE department_id = e.department_id " +
                ") " +
                "GROUP BY d.department_id, e.employee_id, e.first_name, e.last_name, d.department_name, e.salary " +
                "HAVING COUNT(*) = 1  " +
                "ORDER BY d.department_name " +
                "LIMIT 10 OFFSET 20;";
        Statement statement = CCJSqlParserUtil.parse(sql);

        //如果是 select 语句
        if (statement instanceof Select) {
            Select selectStatement = (Select) statement;
            PlainSelect plainSelect = selectStatement.getPlainSelect();
            System.out.println("【DISTINCT 子句】：" + plainSelect.getDistinct());
            System.out.println("【查询字段】：" + plainSelect.getSelectItems());
            System.out.println("【FROM 表】：" + plainSelect.getFromItem());
            System.out.println("【JOIN 子句】：" + plainSelect.getJoins());
            System.out.println("【WHERE 子句】：" + plainSelect.getWhere());
            System.out.println("【GROUP BY 子句】：" + plainSelect.getGroupBy());
            System.out.println("【HAVING 子句】：" +plainSelect.getHaving());
            System.out.println("【ORDER BY 子句】：" + plainSelect.getOrderByElements());
            System.out.println("【LIMIT 子句】：" + plainSelect.getLimit());
            System.out.println("【OFFSET 子句】：" + plainSelect.getOffset());
        }
    }
}

输出：

【DISTINCT 子句】：DISTINCT
【查询字段】：[e.employee_id, e.first_name, e.last_name, d.department_name, e.salary]
【FROM 表】：employees e
【JOIN 子句】：[LEFT JOIN departments d ON e.department_id = d.department_id]
【WHERE 子句】：e.salary > (SELECT AVG(salary) FROM staff WHERE department_id = e.department_id)
【GROUP BY 子句】：GROUP BY d.department_id, e.employee_id, e.first_name, e.last_name, d.department_name, e.salary
【HAVING 子句】：COUNT(*) = 1
【ORDER BY 子句】：[d.department_name]
【LIMIT 子句】： LIMIT 10
【OFFSET 子句】： OFFSET 20

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参考：
JSqlParser实战指南
JSQLParser 解析复杂SQL
JSqlParser入门系列
jsqlparser基本使用