Question

我坦率地说是sql的新手，这是我正在做的一个项目。

我想知道在创建表时是否可以将一个表中的一个列连接到另一个表。我知道显示结果的join方法，但我希望尽可能地减少代码。

CREATE TABLE players ( id INT PRIMARY KEY, -->code I want connect with table match_record player_name CHARACTER ); CREATE TABLE match_records ( (id INT PRIMARY KEY /*FROM players*/), --> the code I want it to be here winner INT, loser INT );

Answer 1

以这种方式：

CREATE TABLE new_table as SELECT id,... from old_table where id = 1;

Answer 2

CREATE TABLE players (
    id INT not null PRIMARY KEY, -->code I want connect with table match_record
    player_name CHARACTER
);

CREATE TABLE match_records (
    id INT not null PRIMARY KEY references players(id),  --> the code I want it to be here
    winner INT,
    loser INT
);

这样您就可以限制match_records.id仅来自players.id：

t=# insert into match_records select 1,1,0;

ERROR:  insert or update on table "match_records" violates foreign key constraint "match_records_id_fkey"
DETAIL:  Key (id)=(1) is not present in table "players".

所以我添加了玩家：

t=# insert into players(id) values(1),(2);
INSERT 0 2

现在它允许插入：

t=# insert into match_records select 1,1,0;
INSERT 0 1

<强>更新 https://www.postgresql.org/docs/current/static/app-psql.html#APP-PSQL-PROMPTING

％＃

如果会话用户是数据库超级用户，则为＃，否则为＆gt;。   （此值的扩展可能会在数据库会话期间更改为   SET SESSION AUTHORIZATION命令的结果。）

如何使用另一个表中的一个现有行创建表？

2 个答案: