2.在表创建好之后添加外键约束 alter table student add constraints pk_student_id PRIMARY key(id); 3.在创建表的语句的最后面使用 constraints pk_表名_字段名 primary key(字段名) 4.删除主键约束alter table student drop constraints pk_student_id; 验证流程: 1-1.创建一张表,在id后加上主键约束 prima...
test=#ALTERTABLEproductsDROPCONSTRAINTproducts_name_uk;ALTERTABLEtest=# \d products;Table"hr.products"Column|Type|Collation|Nullable|Default---+---+---+---+---product_no|integer||notnull|name|text||notnull|price|numeric|||Indexes: "products_pkey"PRIMARYKEY, btree (product_no)Checkconstraint...
ALTER TABLE 表名 ADD CONSTRAINT 约束名 UNIQUE (字段名); 示例: ALTER TABLE students ADD CONSTRAINT unique_email UNIQUE (email); (2)删除唯一约束: 首先需要知道唯一约束的名称,可以通过以下命令查询: SELECT constraint_name FROM information_schema.table_constraints WHERE table_name = '表名' AND constra...
{ FIRST | NEXT } [ count ] { ROW | ROWS } ONLY ] [ FOR { UPDATE | NO KEY UPDATE | SHARE | KEY SHARE } [ OF table_name [, ...] ] [ NOWAIT | SKIP LOCKED ] [...] ] from_item 可以是以下选项之一: [ ONLY ] table_name [ * ] [ [ AS ] alias [ ( column_alias [,...
首先看一下官方解释:Controls the query planner's use of table constraints to optimize queries. The allowed values of constraint_exclusion are on (examine constraints for all tables), off (never examine constraints), and partition (examine constraints only for inheritance child tables and UNION ALL ...
一、主键约束的三种方式1.在字段后加primary key约束id varchar(32) primary key 2.在表创建好之后添加外键约束alter table student add constraints pk_student_id PRIMARY key(id); 3.在创建表的语句的最后面使用 constrain 数据库 python 表名 字段名 ...
PostgreSQL UNIQUE constraint as table constraints SQL CREATE TABLE orders( ord_no integer, ord_date date, item_name character(35), item_grade character(1), ord_qty numeric, ord_amount numeric, UNIQUE (ord_no) ); Output : Constraint data dictionary ...
tco.constraint_name, kcu.ordinal_positionasposition, kcu.column_nameaskey_columnfrominformation_schema.table_constraints tcojoininformation_schema.key_column_usage kcuonkcu.constraint_name=tco.constraint_nameandkcu.constraint_schema=tco.constraint_schemaandkcu.constraint_name=tco.constraint_namewheretco....
.table_constraints AS tc JOIN information_schema.key_column_usage AS kcu ON tc.constraint_name = kcu.constraint_name JOIN information_schema.constraint_column_usage AS ccu ON ccu.constraint_name = tc.constraint_name WHERE constraint_type = 'FOREIGN KEY' AND tc.table_name = 'your table name...
使用下面语句从all_constraints视图中查看某表上的约束: SELECT constraint_name, table_name, r_owner, r_constraint_name...all_constraints WHERE table_name = 'table_name' and owner = 'owner_name'; 另一个视图ALL_CONS_COLUMNS也包括组成表上约束列的信息 ...