PostgreSQL：默认约束名称
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PostgreSQL: default constraint names
提问by Ian Mackinnon
When creating a table in PostgreSQL, default constraint names will assigned if not provided:
在 PostgreSQL 中创建表时，如果未提供，将分配默认约束名称：
CREATE TABLE example (
a integer,
b integer,
UNIQUE (a, b)
);
But using ALTER TABLEto add a constraint it seems a name is mandatory:
但是使用ALTER TABLE添加约束似乎名称是强制性的：
ALTER TABLE example ADD CONSTRAINT my_explicit_constraint_name UNIQUE (a, b);
This has caused some naming inconsistencies on projects I've worked on, and prompts the following questions:
这在我参与的项目中造成了一些命名不一致，并提示以下问题：
Is there a simple way to add a constraint to an extant table with the name it would have received if added during table creation?
If not, should default names be avoided altogether to prevent inconsistencies?
是否有一种简单的方法可以将约束添加到现有表中，其名称是在表创建期间添加时会收到的名称？
如果不是，是否应该完全避免默认名称以防止不一致？
采纳答案by a_horse_with_no_name
回答by Frank Heikens
The standard names for indexes in PostgreSQL are:
PostgreSQL 中索引的标准名称是：
{tablename}_{columnname(s)}_{suffix}
{tablename}_{columnname(s)}_{suffix}
where the suffix is one of the following:
其中后缀是以下之一：
pkeyfor a Primary Key constraintkeyfor a Unique constraintexclfor an Exclusion constraintidxfor any other kind of indexfkeyfor a Foreign keycheckfor a Check constraint
pkey对于主键约束key对于唯一约束excl对于排除约束idx对于任何其他类型的索引fkey对于外键check对于 Check 约束
Standard suffix for sequences is
序列的标准后缀是
seqfor all sequences
seq对于所有序列
Proof of your UNIQUE-constraint:
证明您的 UNIQUE 约束：
NOTICE: CREATE TABLE / UNIQUE will create implicit index "example_a_b_key" for table "example"
注意：CREATE TABLE / UNIQUE 将为表“example”创建隐式索引“example_a_b_key”
