Real MySQL http://www.aladin.co.kr/shop/wproduct.aspx?ISBN=8992939000 책의 455 쪽 Delayed Join 이 정말로 성능이 좋아지는지 테스트하는 코드.

delayedjoin.groovy

@GrabConfig(systemClassLoader=true)
@Grab(group='mysql', module='mysql-connector-java', version='5.1.25')
import groovy.sql.Sql
 
Sql.withInstance('jdbc:mysql://localhost/employees?useUnicode=true&characterEncoding=utf8',
'root', 'root', 'com.mysql.jdbc.Driver') { sql ->
    def times = 1000
    def start = 0

    print "##### 일반 조인 "
    start = System.currentTimeMillis()
    for (i in 1..times) {
        sql.execute("""
            SELECT /*! SQL_NO_CACHE */ e.*
            FROM salaries s, employees e
            WHERE e.emp_no=s.emp_no
                AND s.emp_no BETWEEN 10001 AND 13000
            GROUP BY s.emp_no
            ORDER BY SUM(s.salary) DESC
            LIMIT 10
        """);
    }
    println "  - ${System.currentTimeMillis() - start} ms"

    print "##### 지연된 조인 "

    start = System.currentTimeMillis()
    for (i in 1..times) {
        sql.execute("""
            SELECT /*! SQL_NO_CACHE */ e.*
            FROM
                (SELECT s.emp_no
                FROM salaries s
                WHERE s.emp_no BETWEEN 10001 AND 13000
                GROUP BY s.emp_no
                ORDER BY SUM(s.salary) DESC
                LIMIT 10) x,
                employees e
            WHERE e.emp_no = x.emp_no;
        """);
    }
    println "  - ${System.currentTimeMillis() - start} ms"

}