Question

以下是我开始使用简单求职数据库的代码。当我尝试使用insert语句实际填充数据库时，它会多次添加每一行。

CREATE TABLE IF NOT EXISTS Employers (
  Id INTEGER PRIMARY KEY autoincrement,
  Name VARCHAR(20) NOT NULL,
  Industry VARCHAR(20) NOT NULL,
  Description TEXT
  );

CREATE TABLE IF NOT EXISTS Jobs (
  Id INTEGER PRIMARY KEY autoincrement,
  EmpId INTEGER FOREIGN KEY REFERENCES Employers(Id),
  Title VARCHAR(20) NOT NULL,
  Description TEXT,
  Location VARCHAR(20) NOT NULL,
  Ann_sal INT NOT NULL  
  );

INSERT INTO Employers(Name, Industry, Description )
VALUES 
("Touchpoint Global", "IT", "We help achieve efficiency, reliability and accuracy. 
 We are experts at turning complex inputs into simple outputs.");

INSERT INTO Employers(Name, Industry, Description )
VALUES
("TyTech", "IT", "Here at Tytech, we specialise is building unique business solutions from the ground up. We focus on what you want, and how you want it.");

INSERT INTO Jobs( EmpId, Title, Description, Location, Ann_sal )
SELECT emp.Id, "Project Manager", "Project manager needed to oversee all future projects.", "GoldCoast", 80000
FROM Employers emp
WHERE emp.Name="Tytech";

INSERT INTO Jobs( EmpId, Title, Description, Location, Ann_sal )
SELECT emp.Id, "Project Manager", "Project manager needed to oversee all revolutionary projects.", "Kingscliff", 95000
FROM Employers emp
WHERE emp.Name="Touchpoint Global";

INSERT INTO Jobs( EmpId, Title, Description, Location, Ann_sal )
SELECT emp.Id, "Web Designer", "Web designer needed for upcoming business solution project.", "Kingscliff", 75750
FROM Employers emp
WHERE emp.Name="Touchpoint Global";

INSERT INTO Jobs( EmpId, Title, Description, Location, Ann_sal )
SELECT emp.Id, "Data Analist", "Data analist needed to review input data during testing phases and maintanence.", "Kingscliff", 70000
FROM Employers emp
WHERE emp.Name="Touchpoint Global";

Answer 1

创建适当且有意义的唯一索引可以防止插入不需要的重复项。例如名称和行业，或标题。

Answer 2

您的脚本多次执行。每次重复执行都会插入更多记录。

要确保表为空，可以在INSERT之前添加以下语句：

DELETE FROM Employers;
DELETE FROM Jobs;

但是，为了确保在结构发生更改时更新表，您应该从CREATE TABLE语句中删除IF NOT EXISTS，并确保在这些CREATE TABLE语句之前删除它们：

DROP TABLE IF EXISTS Employers;
DROP TABLE IF EXISTS Jobs;

数据库多次添加行

2 个答案: