常用 SQL介绍

创建表

/*
创建数据表

CREATE TABLE '表名' (
'字段名' 类型(INTEGER, REAL, TEXT, BLOB)
NOT NULL    不允许为空
PRIMARY KEY    主键
AUTOINCREMENT 自增长,
'字段名2' 类型,
...
)

注意：在开发中，如果是从 Navicat 粘贴的 SQL，需要自己添加一个指令
IF NOT EXISTS 加在表名前，如果数据表已经存在，就什么也不做
*/

CREATE TABLE IF NOT EXISTS "T_Person" (
"id" INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
"name" TEXT,
"age" INTEGER,
"heigth" REAL
)

/* 简单约束 */
CREATE TABLE IF NOT EXISTS t_student
(
id INTEGER PRIMARY KEY AUTOINCREMENT,
name TEXT,
age INTEGER
);

CREATE TABLE IF NOT EXISTS t_student
(
id INTEGER PRIMARY KEY AUTOINCREMENT,
name TEXT UNIQUE,
age INTEGER
);

/* 添加主键 */
CREATE TABLE IF NOT EXISTS t_student
(
id INTEGER PRIMARY KEY AUTOINCREMENT,
name TEXT,
age INTEGER,
score REAL
);

/* 添加主键 */
CREATE TABLE IF NOT EXISTS t_student
(
id INTEGER,
name TEXT,
age INTEGER,
score REAL,
PRIMARY KEY(id)
);

插入

INSERT INTO t_student
(age, score, name)
VALUES
('28', 100, 'zhangsan');

INSERT INTO t_student
(name, age)
VALUES
('lisi', '28');

INSERT INTO t_student
(score)
VALUES
(100);

修改

UPDATE t_student
SET name = 'MM'
WHERE age = 10;

UPDATE t_student
SET name = 'WW'
WHERE age is 7;

UPDATE t_student
SET name = 'XXOO'
WHERE age < 20;

UPDATE t_student
SET name = 'NNMM'
WHERE age < 50 and score > 10;

/*更新记录的name*/
UPDATE t_student SET name = 'zhangsan';

删除

DELETE FROM t_student;

DELETE FROM t_student WHERE age < 50;

查询

/* 分页 */
SELECT * FROM t_student
ORDER BY id ASC LIMIT 30, 10;

/* 排序 */
SELECT * FROM t_student
WHERE score > 50
ORDER BY age DESC;

SELECT * FROM t_student
WHERE score < 50
ORDER BY age ASC , score DESC;

/* 计量 */
SELECT COUNT(*)
FROM t_student
WHERE age > 50;

/* 别名 */
SELECT name as myName, age as myAge, score as myScore
FROM t_student;

SELECT name myName, age myAge, score myScore
FROM t_student;

SELECT s.name myName, s.age myAge, s.score myScore
FROM t_student s
WHERE s.age > 50;

/* 查询 */
SELECT name, age, score FROM t_student;
SELECT * FROM t_student;

删除表

/*删除表*/
DROP TABLE IF EXISTS t_student;