SQLite入门之四表的增删?查 (一)

4.1 SQLite 存储类型

SQLite 存储类型

4.2 创建数据库和创建表

创建了一个 COMPANY 表，ID 作为主键，NOT NULL 的约束表示在表中创建纪录时这些字段不能为 NULL

bixiaopeng@bixiaopeng db$ sqlite3 wireless.db
SQLite version 3.7.13 2012-07-17 17:46:21
Enter ".help" for instructions
Enter SQL statements terminated with a ";"
sqlite> CREATE TABLE COMPANY(ID INT PRIMARY KEY NOT NULL,NAME TEXT NOT NULL,AGE INT NOT NULL,ADDRESS CHAR(50),SALARY REAL);

CREATE TABLE 是告诉数据库系统创建一个新表的关键字。CREATE TABLE 语句后跟着表的唯一的名称或标识。您也可以选择指定带有 table_name 的 database_name。

查看表是否创建成功

sqlite> .tables
COMPANY

查看表的完整信息

sqlite> .schema COMPANY
CREATE TABLE COMPANY(ID INT PRIMARY KEY NOT NULL,NAME TEXT NOT NULL,AGE INT NOT NULL,ADDRESS CHAR(50),SALARY REAL);

4.3 插入数据

插入数据，方法一:插入对应的列的值

sqlite> INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY)
   ...> VALUES (1, 'Paul', 32, 'California', 20000.00 );

查询是否插入成功

sqlite> SELECT * FROM COMPANY;
1|Paul|32|California|20000.0

　插入数据，方法二:给所有列插入值

sqlite> INSERT INTO COMPANY VALUES (7, 'James', 24, 'Houston', 10000.00 );
sqlite> SELECT * FROM COMPANY;
1|Paul|32|California|20000.0
7|James|24|Houston|10000.0

用第二种方法多插入几个数据:

sqlite> INSERT INTO COMPANY VALUES (2, 'Allen', 25, 'Texas', 15000.00 );
sqlite> INSERT INTO COMPANY VALUES (3, 'Teddy', 23, 'Norway', 20000.00 );
sqlite> INSERT INTO COMPANY VALUES (4, 'Mark', 25, 'Rich-Mond ', 65000.00 );
sqlite> INSERT INTO COMPANY VALUES (5, 'David', 27, 'Texas', 85000.00 );
sqlite> INSERT INTO COMPANY VALUES (6, 'Kim', 22, 'South-Hall', 45000.00 );
sqlite> SELECT * FROM COMPANY;
1|Paul|32|California|20000.0
7|James|24|Houston|10000.0
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

4.4 更新数据

//先插入一条数据
sqlite> INSERT INTO COMPANY VALUES (8, 'wirelessqa', 28, 'HZ', 20000.00 );
sqlite> SELECT * FROM COMPANY;
ID  NAME    AGE ADDRESS SALARY
1   Paul    32  California  20000.0
7   James   24  Houston 10000.0
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
8   wirelessqa  28  HZ  20000.0

//更新NAME为wirelessqa的地址为NanJing
sqlite> UPDATE COMPANY SET ADDRESS = 'NanJing' WHERE NAME = 'wirelessqa';
8   wirelessqa  28  NanJing 20000.0

//查看更新后的数据
sqlite> SELECT * FROM COMPANY WHERE NAME = 'wirelessqa';
ID  NAME    AGE ADDRESS SALARY
8   wirelessqa  28  NanJing 20000.0

4.5 删除数据

//删除ADDRESS为NanJing的这条数据
sqlite> DELETE FROM COMPANY WHERE ADDRESS = 'NanJing';
sqlite> SELECT * FROM COMPANY WHERE ADDRESS = 'NanJing';
sqlite>

4.6　数据查询

4.6.1. SQLite 算术运算符

运算符: + - * / %

sqlite> select 4 + 2;
6
sqlite> select 4 - 2;
2
sqlite> select 4 * 2;
8
sqlite> select 4 / 2;
2
sqlite> select 4 % 2;
0

4.6.2. SQLite 算术运算符

看一下表里现有的数据：

sqlite> .