在PostgreSQL中创建唯一键(Unique Key)可以通过添加唯一约束(Unique Constraint)来实现。以下是详细的步骤和示例代码,用于指导如何在PostgreSQL中创建唯一键: 1. 确定要在哪个表上创建唯一键 假设我们有一个名为employees的表,我们希望在这个表上创建一个唯一键。 2. 确定唯一键包含的列 假设我们希望在employees表的ema...
ADD [ COLUMN ] [ IF NOT EXISTS ] column_name data_type [ COLLATE collation ] [ column_constraint [ ... ] ] DROP [ COLUMN ] [ IF EXISTS ] column_name [ RESTRICT | CASCADE ] ALTER [ COLUMN ] column_name [SETDATA ]TYPEdata_type [ COLLATE collation ] [ USING expression ] ALTER [...
cwt=>\d+sale_detail Partitionedtable"public.sale_detail"Column|Type|Collation|Nullable|Default|Storage|Compression|Stats target|Description---+---+---+---+---+---+---+---+---product_id
AI代码解释 postgres=# create tabletest(id serial primary key,name varchar unique);CREATETABLEpostgres=# \d test Table"public.test"Column|Type|Collation|Nullable|Default---+---+---+---+---id|integer||notnull|nextval('test_id_seq'::regclass)name|character varying|||Indexes:"test_pkey"PRI...
"products_name_uk"UNIQUECONSTRAINT, btree (name)Checkconstraints: "products_price_min"CHECK(price>0::numeric) test=#ALTERTABLEproductsALTERCOLUMNnameSETNOTNULL;ALTERTABLEtest=# \d products;Table"hr.products"Column|Type|Collation|Nullable|Default---+---+---+---+---product_no|integer||notnull...
postgres=#\dpg_stat_ioView"pg_catalog.pg_stat_io"Column|Type|Collation|Nullable|Default---+---+---+---+---backend_type|text|||object|text|||context|text|||reads|bigint|||read_time|doubleprecision|||writes|bigint|||write_time|doubleprecision|||writebacks|bigint|||writeback_time|d...
Column | Type | Collation | Nullable | Default ---+---+---+---+--- a | integer | | | b | text | | | Indexes: "i" btree (b) postgres=# select relpages,reltuples from pg_class where relname = 't'; relpages | reltuples ---+--- 1 | 100 (1...
Partitioned tables do not support UNIQUE, PRIMARY KEY, EXCLUDE, or FOREIGN KEY constraints; however, you can define these constraints on individual partitions. When using range partitioning, a NOT NULL constraint is added to each non-expression column in the partition key. ...
Support unique constraints on nullable columns. Escape hatch babelfishpg_tsql.escape_hatch_unique_constraint has been deprecated. Critical stability enhancements Fixed issue producing syntax error with delimited column alias without preceding whitespace. Creating a user for a login is blocked when its lo...
Partition constraint: ((status IS NOT NULL) AND (status = ANY (ARRAY['EXPIRED1'::text, 'EXPIRED2'::text]))) Indexes: "cust_archived_arr_idx" btree (arr) Access method: heap postgres=# \d+ cust_others Table "public.cust_others" Column | Type | Collation | Nullable | Default | St...