1. Create a database table
Face SQLite database, before we are familiar with SQL commands can be used:
>>> create_table = "create table books (title,author,language)"
>>> cur.execute(create_table)
<sqlite3.Cursor object at 0x104f296c0>
This will set up a table in the database lite.db in books. Data can be added to this table:
>>> cur.execute('insert into books values("python basic","rocky","python")')
<sqlite3.Cursor object at 0x104f296c0>In order to ensure that data can be saved, but also the following operations:
>>> conn.commit()
>>> cur.close()
>>> conn.close()Above, the database already has just created a table books, the table already has a record.
2. Query
After saving Let's check what:
>>> conn = sqlite3.connect('lite.db')
>>> cur = conn.cursor()
>>> cur.execute('select * from books')
<sqlite3.Cursor object at 0x104f297a0>
>>> cur.fetchall()[('python basic', 'rocky', 'python')]3. Bulk Insert
We come to the table books add some more content, in order to carry out other operations to us:
>>> books = [("first book","first","c"),("second book","second","c++"),("third book","third","java")]This time we come to a bulk insert:
>>> cur.executemany('insert into books values (?,?,?)',books)
<sqlite3.Cursor object at 0x104f297a0>
>>> conn.commit()Next we print it with a loop to query results:
>>> rows = cur.execute('select * from books')
>>> for row in rows:
... print(row)
... ('python basic', 'rocky', 'python')('first book', 'first', 'c')('second book', 'second', 'c++')('third book', 'third', 'java')
4. Update
As we said earlier, in cur.execute (), you can write SQL statements to manipulate database:
>>> cur.execute("update books set title='physics' where author='first'")
<sqlite3.Cursor object at 0x104f297a0>
>>> conn.commit()Then we follow the conditions of inquiry to look at:
>>> cur.execute("select * from books where author='first'")
<sqlite3.Cursor object at 0x104f297a0>
>>> cur.fetchall()[('physics', 'first', 'c')]
5. Delete
Operation of the database must also delete the action:
>>> cur.execute("select * from books")
<sqlite3.Cursor object at 0x104f297a0>
>>> cur.fetchall()
[('python basic', 'rocky', 'python'), ('physics', 'first', 'c'), ('third book', 'third', 'java')]
Finally, do not forget that after the completion of operation of the database, people must remember to "shut the door":
>>> cur.close()
>>> conn.close()
conn.execute('''CREATE TABLE MT
(ID INT PRIMARY KEY NOT NULL,
NAME TEXT NOT NULL,
AGE INT NOT NULL,
ADDRESS CHAR(50),
SALARY REAL);''')
除此之外，select语句还可以搭配一些SQLite功能函数使用，常用的有：
count(*) 统计表内行数（记录数） sqlite> select count(*) from stu;
max(column) 计算该列的最大值 columen 是一列的名字
min(column) 计算该列的最小值
avg(column) 计算该列的平均值
sum(column) 计算该列的总和
upper(column) 输出选中的列的所有字符串的全大写字母
lower(column) 输出选中的列的所有字符串的全小写字母
length(column) 计算该列的所有字符串的长度
将这些函数放在select语句内可以完成一些计算工作。例如输入命令
select sum(score) from student;
可以求出表student内所有学生的成绩总和。
8、模糊查询——like子句
除了使用where子句设定筛选条件外，我们还可以使用like子句模糊匹配表内的记录。like语句搭配两个通配符一起使用：
百分号% 表示零个、一个或多个数字或字符
下划线_ 表示一个数字或字符
如果某条记录内的某一列能与like后的条件匹配，则该记录被选定。例如：
select * from student where name like %l%;//从表student中选取名字内带字母l的所有记录
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原文：https://blog.csdn.net/nan_lei/article/details/84344003