[SQL]-(109) WITH절 사용하기1

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[Reference] 초보자를 위한 SQL 200제

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[SQL 문법]

동일한 SQL이 반복되어 사용될 때 성능을 높일 수 있다.

WITH JOB_SUMSAL AS (SELECT JOB, SUM(SAL) as total
                        FROM EMP
                        GROUP BY JOB)
    SELECT JOB, total
      FROM JOB_SUMSAL
      WHERE total > (SELECT AVG(total)
                          FROM JOB_SUMSAL)

[예시]

# 오라클 연동 및 접속
import pandas as pd
import cx_Oracle
dsn=cx_Oracle.makedsn('localhost',1521,'orcl')
db=cx_Oracle.connect('scott','tiger')
cursor=db.cursor()

# SQL 문법
cursor.execute("""
WITH JOB_SUMSAL AS (SELECT JOB, SUM(SAL) as total
                        FROM EMP
                        GROUP BY JOB)
    SELECT JOB, total
      FROM JOB_SUMSAL
      WHERE total > (SELECT AVG(total)
                          FROM JOB_SUMSAL)
"""
)

row=cursor.fetchall()
colname=cursor.description
col=[]

for i in colname:
    col.append(i[0])

# pandas를 사용한 데이터 프레임 형식으로 변환
emp=pd.DataFrame(row,columns=col)
print(emp)

[결과]

       JOB  TOTAL
0  MANAGER   8275
1  ANALYST   6500