📅 最后修改于: 2020-11-06 05:57:19 🧑 作者: Mango
UPDATE对任何数据库的操作都意味着修改表中一个或多个记录的值，这些值已经在数据库中可用。您可以使用UPDATE语句更新SQLite中现有记录的值。
要更新特定的行，您需要与其一起使用WHERE子句。
以下是SQLite中UPDATE语句的语法-
UPDATE table_name
SET column1 = value1, column2 = value2...., columnN = valueN
WHERE [condition];
假设我们使用以下查询创建了一个名为CRICKETERS的表-
sqlite> CREATE TABLE CRICKETERS (
First_Name VARCHAR(255),
Last_Name VARCHAR(255),
Age int,
Place_Of_Birth VARCHAR(255),
Country VARCHAR(255)
);
sqlite>
如果我们使用INSERT语句将5条记录插入其中-
sqlite> insert into CRICKETERS values('Shikhar', 'Dhawan', 33, 'Delhi', 'India');
sqlite> insert into CRICKETERS values('Jonathan', 'Trott', 38, 'CapeTown', 'SouthAfrica');
sqlite> insert into CRICKETERS values('Kumara', 'Sangakkara', 41, 'Matale', 'Srilanka');
sqlite> insert into CRICKETERS values('Virat', 'Kohli', 30, 'Delhi', 'India');
sqlite> insert into CRICKETERS values('Rohit', 'Sharma', 32, 'Nagpur', 'India');
sqlite>
以下声明修改了板球运动员的年龄，该板球运动员的名字为Shikhar-
sqlite> UPDATE CRICKETERS SET AGE = 45 WHERE FIRST_NAME = 'Shikhar' ;
sqlite>
如果您检索FIRST_NAME是Shikhar的记录，则会观察到年龄值已更改为45-
sqlite> SELECT * FROM CRICKETERS WHERE FIRST_NAME = 'Shikhar';
First_Name Last_Name Age Place_Of_B Country
---------- ---------- ---- ---------- --------
Shikhar Dhawan 45 Delhi India
sqlite>
如果您还没有使用过WHERE子句，则所有记录的值都会被更新。以下UPDATE语句使CRICKETERS表中的所有记录的寿命增加1-
sqlite> UPDATE CRICKETERS SET AGE = AGE+1;
sqlite>
如果使用SELECT命令检索表的内容，则可以看到更新后的值为-
sqlite> SELECT * FROM CRICKETERS;
First_Name Last_Name Age Place_Of_B Country
---------- ---------- ---- ---------- -------------
Shikhar Dhawan 46 Delhi India
Jonathan Trott 39 CapeTown SouthAfrica
Kumara Sangakkara 42 Matale Srilanka
Virat Kohli 31 Delhi India
Rohit Sharma 33 Nagpur India
sqlite>
要将记录添加到SQLite数据库中的现有表中-
导入sqlite3包。
通过将数据库名称作为参数传递给它，使用connect()方法创建一个连接对象。
cursor()方法返回一个游标对象，您可以使用该对象与SQLite3进行通信。通过调用(上面创建的)Connection对象上的cursor()对象来创建光标对象。
然后，通过向游标对象传递UPDATE语句作为参数来调用execute()方法。
在Python示例中，创建一个名为EMPLOYEE的表，向其中插入5条记录，并使所有男性雇员的年龄增加1-
import sqlite3
#Connecting to sqlite
conn = sqlite3.connect('example.db')
#Creating a cursor object using the cursor() method
cursor = conn.cursor()
#Doping EMPLOYEE table if already exists.
cursor.execute("DROP TABLE IF EXISTS EMPLOYEE")
#Creating table as per requirement
sql ='''CREATE TABLE EMPLOYEE(
FIRST_NAME CHAR(20) NOT NULL,
LAST_NAME CHAR(20),
AGE INT,
SEX CHAR(1),
INCOME FLOAT
)'''
cursor.execute(sql)
#Inserting data
cursor.execute('''INSERT INTO EMPLOYEE(FIRST_NAME, LAST_NAME, AGE, SEX, INCOME)
VALUES ('Ramya', 'Rama priya', 27, 'F', 9000),
('Vinay', 'Battacharya', 20, 'M', 6000),
('Sharukh', 'Sheik', 25, 'M', 8300),
('Sarmista', 'Sharma', 26, 'F', 10000),
('Tripthi', 'Mishra', 24, 'F', 6000)''')
conn.commit()
#Fetching all the rows before the update
print("Contents of the Employee table: ")
cursor.execute('''SELECT * from EMPLOYEE''')
print(cursor.fetchall())
#Updating the records
sql = '''UPDATE EMPLOYEE SET AGE=AGE+1 WHERE SEX = 'M' '''
cursor.execute(sql)
print("Table updated...... ")
#Fetching all the rows after the update
print("Contents of the Employee table after the update operation: ")
cursor.execute('''SELECT * from EMPLOYEE''')
print(cursor.fetchall())
#Commit your changes in the database
conn.commit()
#Closing the connection
conn.close()
Contents of the Employee table:
[
('Ramya', 'Rama priya', 27, 'F', 9000.0),
('Vinay', 'Battacharya', 20, 'M', 6000.0),
('Sharukh', 'Sheik', 25, 'M', 8300.0),
('Sarmista', 'Sharma', 26, 'F', 10000.0),
('Tripthi', 'Mishra', 24, 'F', 6000.0)
]
Table updated......
Contents of the Employee table after the update operation:
[
('Ramya', 'Rama priya', 27, 'F', 9000.0),
('Vinay', 'Battacharya', 21, 'M', 6000.0),
('Sharukh', 'Sheik', 26, 'M', 8300.0),
('Sarmista', 'Sharma', 26, 'F', 10000.0),
('Tripthi', 'Mishra', 24, 'F', 6000.0)
]