slqite3练习

连接

import sqlite3


con = sqlite3.connect(":memory:")

c = con.cursor()

# Create table
c.execute('''CREATE TABLE COMPANY
            (ID integer, NAME text, AGE integer, ADDRESS text, SALARY real)''')

# Larger example that inserts many records at a time
purchases = [(1,'Paul',32,'California',20000.0),
             (2,'Allen',25,'Texas',15000.0),
             (3,'Teddy',23,'Norway',20000.0),
             (4,'Mark',25,'Rich-Mond',65000.0),
             (5,'David',27,'Texas',85000.0),
             (6,'Kim',22,'South-Hall',45000.0),
             (7,'James',24,'Houston',10000.0)]
c.executemany('INSERT INTO COMPANY VALUES (?,?,?,?,?)', purchases)



# Create table
c.execute('''CREATE TABLE DEPARTMENT(
               ID INT PRIMARY KEY      NOT NULL,
               DEPT           CHAR(50) NOT NULL,
               EMP_ID         INT      NOT NULL
            );''')

# Larger example that inserts many records at a time
purchases = [(1, 'IT Billing', 1 ),
             (2, 'Engineering', 2 ),
             (3, 'Finance', 7 )]
c.executemany('INSERT INTO DEPARTMENT VALUES (?,?,?)', purchases)


# Save (commit) the changes
con.commit()

# 显示所有记录
c.execute("SELECT * FROM COMPANY;")
for row in c:
    print(row)

print()
# 显示所有记录
c.execute("SELECT * FROM DEPARTMENT;")
for row in c:
    print(row)

print("
连接（JOIN）")
c.execute("SELECT * FROM COMPANY,DEPARTMENT;")
for row in c:
    print(row)    

print("
交叉连接（CROSS JOIN）")
#c.execute("SELECT EMP_ID, NAME, DEPT FROM COMPANY CROSS JOIN DEPARTMENT;")
c.execute("SELECT * FROM COMPANY CROSS JOIN DEPARTMENT;")
for row in c:
    print(row)

print("
内连接（INNER JOIN）")
c.execute("SELECT EMP_ID, NAME, DEPT FROM COMPANY INNER JOIN DEPARTMENT ON COMPANY.ID = DEPARTMENT.EMP_ID;")
for row in c:
    print(row)

print("
左外连接（LEFT OUTER JOIN）")
c.execute("SELECT EMP_ID, NAME, DEPT FROM COMPANY LEFT OUTER JOIN DEPARTMENT ON COMPANY.ID = DEPARTMENT.EMP_ID;")
for row in c:
    print(row)

子查询

import sqlite3

'''子查询'''


con = sqlite3.connect(":memory:")

c = con.cursor()

# Create table
c.execute('''CREATE TABLE COMPANY
            (ID integer, NAME text, AGE integer, ADDRESS text, SALARY real)''')

# Larger example that inserts many records at a time
purchases = [(1,'Paul',32,'California',20000.0),
             (2,'Allen',25,'Texas',15000.0),
             (3,'Teddy',23,'Norway',20000.0),
             (4,'Mark',25,'Rich-Mond',65000.0),
             (5,'David',27,'Texas',85000.0),
             (6,'Kim',22,'South-Hall',45000.0),
             (7,'James',24,'Houston',10000.0)]
c.executemany('INSERT INTO COMPANY VALUES (?,?,?,?,?)', purchases)


# Save (commit) the changes
con.commit()


# ====================================================================================
# SELECT 语句中的子查询使用
# ====================================================================================
print('='*30)
print('SELECT 语句中的子查询使用')
print('='*30)


c.execute("SELECT * "
         "FROM COMPANY "
         "WHERE ID IN (SELECT ID "
                      "FROM COMPANY "
                      "WHERE SALARY > 45000);")
                      
for row in c:
    print(row)

# ====================================================================================
# INSERT 语句中的子查询使用
# ====================================================================================
print('='*30)
print('INSERT 语句中的子查询使用')
print('='*30)

# Create table
c.execute('''CREATE TABLE COMPANY_BKP
            (ID integer, NAME text, AGE integer, ADDRESS text, SALARY real)''')
            
c.execute("INSERT INTO COMPANY_BKP "
         "SELECT * FROM COMPANY "
         "WHERE ID IN (SELECT ID "
                      "FROM COMPANY);")
                      
c.execute("SELECT * FROM COMPANY_BKP")
for row in c:
    print(row)
    
# ====================================================================================
# UPDATE 语句中的子查询使用
# ====================================================================================
print('='*30)
print('UPDATE 语句中的子查询使用')
print('='*30)

# 子查询
c.execute("UPDATE COMPANY_BKP "
         "SET SALARY = SALARY * 0.50 "
         "WHERE AGE IN (SELECT AGE FROM COMPANY_BKP "
                       "WHERE AGE >= 27 );")
                       
c.execute("SELECT * FROM COMPANY_BKP")           
for row in c:
    print(row)
    
# ====================================================================================
# DELETE 语句中的子查询使用
# ====================================================================================
print('='*30)
print('DELETE 语句中的子查询使用')
print('='*30)

# 子查询
c.execute("DELETE FROM COMPANY_BKP "
         "WHERE AGE IN (SELECT AGE FROM COMPANY_BKP "
                       "WHERE AGE > 27 );")

c.execute("SELECT * FROM COMPANY_BKP")
for row in c:
    print(row)
    

c.execute("SELECT tbl_name FROM :memory: WHERE type = 'table';")