The PostgreSQL FOREIGN KEY is a combination of columns with values based on the primary key values from another table. A foreign key constraint, also known as Referential integrity Constraint, specifies that the values of the foreign key correspond to actual values of the primary key in the othe...
CREATE TABLE orders ( order_id integer PRIMARY KEY, product_no integer REFERENCES products, quantity integer ); # 定义多个 Column 组成的外键,要求被约束列(外键)的数量和类型应该匹配被引用列(主键)的数量和类型。 CREATE TABLE t1 ( a integer PRIMARY KEY, b integer, c integer, FOREIGN KEY (b, ...
constraint_type有四种:UNIQUE、PRIMARY KEY、CHECK、FOREIGN KEY 通过修改上边sql语句的table_name和constraint_type来进行相应的查询 警告
CREATE TABLE parent(key integer, ...); CREATE TABLE child1000(check (key between 1000 and 1999)) INHERITS(parent); CREATE TABLE child2000(check (key between 2000 and 2999)) INHERITS(parent); SELECT * FROM parent WHERE key = 2400; 在启用约束排除时,这个SELECT将完全不会扫描child1000,从而提...
"tbl_pkey"PRIMARYKEY, btree (id) Referencedby:TABLE"tbl1"CONSTRAINT"tbl1_id_fkey"FOREIGNKEY (id)REFERENCEStbl(id) postgres=# \d tbl1Table"public.tbl1"Column|Type|Modifiers---+---+---id|integer|info|text|Foreign-key constraints: "tbl1_id_fkey"FOREIGNKEY (id...
In this post, I am sharing one option to Disable / Enable the Foreign Key Constraint in PostgreSQL. During data migration and testing purpose, Database Developer requires to disable Foreign key constraint of a Table. Once you disable constraint, then later you might need t...
包含PRIMARY KEY、UNIQUE KEY、FOREIGN KEY、DATATYPE(内置数据类型)和DEFAULT CONSTRAINT。 VIEW、PROCEDURE(PostgreSQL的版本需为11及以上)、FUNCTION、RULE、SEQUENCE、EXTENSION、TRIGGER、AGGREGATE、INDEX、OPERATOR、DOMAIN 支持同步的SQL操作 操作类型 SQL操作语句 DML INSERT、UPDATE、DELETE DDL 仅2020...
Support for new INFORMATION_SCHEMA catalogs: COLUMN_DOMAIN_USAGE, CONSTRAINT_COLUMN_USAGE, CHECK_CONSTRAINTS, ROUTINES, VIEWS. Support for new PG-style query plan: escape hatch 'babelfish_pgtsql.escape_hatch_showplan_all'. when set to 'ignore', SET SHOWPLAN_ALL and SET STATISTICS PROFILE behaves...
Which type of data a table can store that may be decided by the type of data. That is why CONSTRAINTS needed. Suppose the age of a student is always be a positive value but there is no such data type which can accept the only positive value, a CONSTRAINT can do this. ...
在原表上update,新临时表上是replace into整行数据,所以达到有则更新,无则插入。同时配合后面的 insert ignore,保证这条数据不会因为重复而失败。 3.3 为什么外键那么特殊 假设t1是要修改的表,t2有外键依赖于t1,_t1_new是 altert1产生的新临时表。