[SQL] SQL 基础知识梳理（七）- 集合运算

一、表的加减法

　　1.集合：记录的集合（表、视图和查询的执行结果）。

　　2.UNION（并集）：表的加法

-- DDL：创建表
CREATE TABLE Shohin2
(shohin_id     CHAR(4)      NOT NULL,
 shohin_mei    VARCHAR(100) NOT NULL,
 shohin_bunrui VARCHAR(32)  NOT NULL,
 hanbai_tanka  INTEGER      ,
 shiire_tanka  INTEGER      ,
 torokubi      DATE         ,
 PRIMARY KEY (shohin_id));

-- DML：插入数据

INSERT INTO Shohin2 VALUES ('0001', 'T恤' ,'衣服', 1000, 500, '2009-09-20');
INSERT INTO Shohin2 VALUES ('0002', '打孔器', '办公用品', 500, 320, '2009-09-11');
INSERT INTO Shohin2 VALUES ('0003', '运动T恤', '衣服', 4000, 2800, NULL);
INSERT INTO Shohin2 VALUES ('0009', '手套', '衣服', 800, 500, NULL);
INSERT INTO Shohin2 VALUES ('0010', '水壶', '厨房用具', 2000, 1700, '2009-09-20');

CREATE TABLE Shohin
(shohin_id     CHAR(4)      NOT NULL,
 shohin_mei    VARCHAR(100) NOT NULL,
 shohin_bunrui VARCHAR(32)  NOT NULL,
 hanbai_tanka  INTEGER ,
 shiire_tanka  INTEGER ,
 torokubi      DATE ,
 PRIMARY KEY (shohin_id));

INSERT INTO Shohin VALUES ('0001', 'T恤' ,'衣服', 1000, 500, '2009-09-20');
INSERT INTO Shohin VALUES ('0002', '打孔器', '办公用品', 500, 320, '2009-09-11');
INSERT INTO Shohin VALUES ('0003', '运动T恤', '衣服', 4000, 2800, NULL);
INSERT INTO Shohin VALUES ('0004', '菜刀', '厨房用具', 3000, 2800, '2009-09-20');
INSERT INTO Shohin VALUES ('0005', '高压锅', '厨房用具', 6800, 5000, '2009-01-15');
INSERT INTO Shohin VALUES ('0006', '叉子', '厨房用具', 500, NULL, '2009-09-20');
INSERT INTO Shohin VALUES ('0007', '擦菜板', '厨房用具', 880, 790, '2008-04-28');
INSERT INTO Shohin VALUES ('0008', '圆珠笔', '办公用品', 100, NULL, '2009-11-11');

初始化测试数据

目录

一、表的加减法