错误：关系“学生”已经存在

Question

当我执行此查询时：

CREATE TABLE public.students (
  id INTEGER PRIMARY KEY NOT NULL DEFAULT NEXTVAL('students_id_seq'::regclass),
  first_name CHARACTER VARYING(20) NOT NULL,
  last_name CHARACTER VARYING(20) NOT NULL,
  major CHARACTER VARYING(20) NOT NULL
);
CREATE UNIQUE INDEX "Students_ID_uindex" ON students USING BTREE (id);

SELECT * FROM public.students;

我收到以下错误：

[2016-03-12 22:16:54] Run postgres.public.students [PostgreSQL - postgres@localhost]
[2016-03-12 22:16:54] Connecting TO PostgreSQL - postgres@localhost...
CREATE TABLE public.students (
  id INTEGER PRIMARY KEY NOT NULL DEFAULT NEXTVAL('students_id_seq'::regclass),
  first_name CHARACTER VARYING(20) NOT NULL,
  last_name CHARACTER VARYING(20) NOT NULL,
  major CHARACTER VARYING(20) NOT NULL
)
[2016-03-12 22:16:54] [42P07] ERROR: relation "students" already EXISTS
CREATE UNIQUE INDEX "Students_ID_uindex" ON students USING BTREE (id)
[2016-03-12 22:16:54] [42P07] ERROR: relation "Students_ID_uindex" already EXISTS
SELECT * FROM public.students
[2016-03-12 22:16:54] Executed IN 14ms ms

[2016-03-12 22:16:54] Summary: 3 OF 3 statements executed, 2 failed IN 68ms (338 symbols IN file)

我已经使用 DataGrip 生成了表格：

知道我做错了什么吗？

更新：只是为了澄清我的问题，当我第一次使用新表名运行代码时，我现在得到错误但是当我再次运行它时我得到上述错误。如何解决这个问题？

Answer 1

您不能创建更多具有相同名称的表 - 因此CREATE如果已经存在具有相同名称的表，则语句应该失败。

您可以在DROP TABLE之前运行该语句- 但请注意！- 它删除包含所有数据的表，并且无法撤消。第二种选择是IF NOT EXISTS在CREATE语句中使用子句：

DROP TABLE IF EXISTS foo;
CREATE TABLE foo(a int);

或者

CREATE TABLE IF NOT EXISTS foo(a int);