To define a foreign key, you can use a foreign key constraint. PostgreSQL foreign key constraint syntax The following illustrates a foreign key constraint syntax: [CONSTRAINT fk_name] FOREIGN KEY(fk_columns) RE
CREATE TABLE orders ( order_id SERIAL PRIMARY KEY, user_id INT NOT NULL, order_date DATE NOT NULL, FOREIGN KEY (user_id) REFERENCES users(user_id) ON DELETE CASCADE ); 手动处理:在删除前手动处理引用表中的记录。 代码语言:txt 复制
Command:CREATETRIGGERDescription:define anewtriggerSyntax:CREATE[CONSTRAINT]TRIGGERname{BEFORE|AFTER|INSTEADOF}{event[OR...]}ONtable_name[FROMreferenced_table_name]{NOTDEFERRABLE|[DEFERRABLE]{INITIALLYIMMEDIATE|INITIALLYDEFERRED}}[FOR[EACH]{ROW|STATEMENT}][WHEN(condition)]EXECUTEPROCEDUREfunction_name(argume...
You’ll start by analyzing the business requirements, identifying tables and relationships, and creating tables with primary and foreign keys. Database design –Start designing a database for the inventory management system from scratch. Primary key –Show you how to define a primary key for a ...
ALTER TABLE rental ADD CONSTRAINT fk_customer_id FOREIGN KEY (customer_id) REFERENCES customers(customer_id); 6. Exclusion Constraints:Exclusion constraints ensure that no two rows in a table satisfy a specified predicate. This allows you to define custom constraints beyond simple unique or check ...
Foreign key –show you how to define foreign key constraints when creating a new table or adding foreign key constraints for existing tables. DELETE CASCADE –show you how to automatically delete rows in child tables when the corresponding rows in the parent table are deleted. CHECK constraint –...
-D, --define=VARNAME=VALUE define variableforuse by custom script -j, --jobs=NUM number of threads (default: 1) -l, --logwrite transactiontimestologfile -L, --latency-limit=NUM count transactions lasting more than NUM ms as late ...
(v_table_oidISNULL)THENRAISE EXCEPTION'table does not exist';ENDIF;-- start the create definitionv_table_ddl :='CREATE TABLE "'||in_table_name||'" ('||E'\n';-- define all of the columns in the table; https://stackoverflow.com/a/8153081/3068233FORv_column_recordINSELECTc.column...
postgres=#\helpcreatetablespace;Command:CREATETABLESPACEDescription:defineanewtablespaceSyntax:CREATETABLESPACEtablespace_name[OWNER{new_owner|CURRENT_ROLE|CURRENT_USER|SESSION_USER}]LOCATION'directory'[WITH(tablespace_option=value[,...])]--创建表空间abc_tbs,实现准备对应的目录[postgres@centos79~]$ls-lrt...
CREATE TABLE EMPLOYEES ( EMPLOYEE_ID NUMBER PRIMARY KEY, FIRST_NAME VARCHAR2(20) NOT NULL, LAST_NAME VARCHAR2(25) NOT NULL, EMAIL VARCHAR2(25), DEPARTMENT_ID NUMBER); REF constraints REF constraints define a relationship between a column of type REF and the object ...