常用 SQL介绍

最新推荐文章于 2023-06-15 20:51:12 发布

Jack-Zeng

最新推荐文章于 2023-06-15 20:51:12 发布

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分类专栏： SQLite的使用(Swift) 文章标签： sqlite iOS

本文链接：https://blog.youkuaiyun.com/dazeng1990/article/details/50901608

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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;