如何在 PostgreSQL 中提取 table 的唯一列的名称？

Question

假设我在 PorstreSQL 中有一个 table 定义为：

CREATE TABLE my_table (
  id serial not null primary key,
  var1 text null,
  var2 text null unique,
  var3 text null,
  var4 text null unique
);

是否有对 information_schema 的查询仅提供唯一列的名称？理想的回应应该是：

var2
var4

查询应该同时忽略多个列的唯一键。

Answer 1

您需要 information_schema.table_constraints 和 information_schema.constraint_column_usage:

SELECT table_schema, table_name, column_name
FROM information_schema.table_constraints AS c
   JOIN information_schema.constraint_column_usage AS cc
      USING (table_schema, table_name, constraint_name)
WHERE c.constraint_type = 'UNIQUE';

如果要跳过多列约束，请使用分组：

SELECT table_schema, table_name, min(column_name)
FROM information_schema.table_constraints AS c
   JOIN information_schema.constraint_column_usage AS cc
      USING (table_schema, table_name, constraint_name)
WHERE c.constraint_type = 'UNIQUE'
GROUP BY table_schema, table_name
HAVING count(*) = 1;

如何在 PostgreSQL 中提取 table 的唯一列的名称？

How to extract the names of unique columns of a table in PostgreSQL?

postgresql

information-schema