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Our goal is that when a record is inserted in employee table, we also want this record to be inserted in employee_backup table.Our example will have two tables: employee and employee_backup.--Disk-Based CREATE TABLE Syntax CREATE TABLE [ database_name . For more information about File Tables, see File Tables (SQL Server). ] table_name [ AS File Table ] ( [ ,...n ] [ PERIOD FOR SYSTEM_TIME ( system_start_time_column_name , system_end_time_column_name ) ] ) [ ON ] [ TEXTIMAGE_ON ] [ FILESTREAM_ON ] [ WITH ( [ FILESTREAM ] [ COLLATE collation_name ] [ SPARSE ] [ MASKED WITH ( FUNCTION = ' mask_function ') ] [ CONSTRAINT constraint_name [ DEFAULT constant_expression ] ] [ IDENTITY [ ( seed,increment ) ] [ NOT FOR REPLICATION ] [ GENERATED ALWAYS AS ROW [ HIDDEN ] ] [ NULL | NOT NULL ] [ ROWGUIDCOL ] [ ENCRYPTED WITH ( COLUMN_ENCRYPTION_KEY = key_name , ENCRYPTION_TYPE = , ALGORITHM = ' AEAD_AES_256_CBC_HMAC_SHA_256' ) ] [ [ , ...n ] ) ] [ ON ] | [ FOREIGN KEY ] REFERENCES referenced_table_name [ ( ref_column ) ] [ ON DELETE ] [ ON UPDATE ] [ NOT FOR REPLICATION ] | CHECK [ NOT FOR REPLICATION ] ( logical_expression ) ] [ , ...n ] ) ] [ ON ] | FOREIGN KEY ( column [ ,...n ] ) REFERENCES referenced_table_name [ ( ref_column [ ,...n ] ) ] [ ON DELETE ] [ ON UPDATE ] [ NOT FOR REPLICATION ] | CHECK [ NOT FOR REPLICATION ] ( logical_expression ) --Memory optimized CREATE TABLE Syntax CREATE TABLE [database_name . AS File Table Applies to: SQL Server 2012 through SQL Server 2017. You do not specify columns because a File Table has a fixed schema.We will create these tables and populate them with some data./*Check whether or not employee table already exists*/ IF OBJECT_ID('EMPLOYEE') IS NOT NULL DROP TABLE EMPLOYEE GO /* Create employee table if it does not exist */ CREATE TABLE EMPLOYEE ( EMPID INT PRIMARY KEY, FNAME VARCHAR(25), LNAME VARCHAR(25), ) GO /* Populate employee table with sample rows */ INSERT INTO EMPLOYEE (EMPID, FNAME, LNAME) VALUES (500, 'John','Smith'), (501, 'Alex','Admas'), (502, 'Eric','James'), (503, 'Shaun','Marsh') GO /* Create and sync employee_backup table with records from employee table so that both tables will have the same records */ IF OBJECT_ID('EMPLOYEE_BACKUP') IS NOT NULL DROP TABLE EMPLOYEE_BACKUP GO SELECT * INTO EMPLOYEE_BACKUP FROM EMPLOYEE GO /* See the table records from both tables.-- Create 3 tables with the same schema: create table Table_1 (Col_1 int identity (1,1) PRIMARY KEY, Col_2 varchar(10) NOT NULL, Col_3 datetime NOT NULL default getdate()) go select convert(int, Col_1) as Col_1, -- I use the convert to eliminate the Identity property.Col_2, Col_3 into Table_2 from Table_1 go select convert(int, Col_1) as Col_1, Col_2, Col_3 into Table_3 from Table_1 go -- Truncate 3 tables truncate table Table_1 truncate table Table_2 truncate table Table_3 go -- Clean SQL SERVER memory: dbcc dropcleanbuffers go -- Run 10000 inserts declare @i int set @i = 1 while @i -- Create one trigger with two inserts: create trigger trg_I_Table_1 ON Table_1 FOR INSERT as insert into Table_2 (Col_1, Col_2, Col_3) select Col_1, Col_2, Col_3 from inserted insert into Table_3 (Col_1, Col_2, Col_3) select Col_1, Col_2, Col_3 from inserted go -- Create two triggers – one with each command: create trigger trg1_I_Table_1 ON Table_1 FOR INSERT as insert into Table_2 (Col_1, Col_2, Col_3) select Col_1, Col_2, Col_3 from inserted go create trigger trg2_I_Table_1 ON Table_1 FOR INSERT as insert into Table_3 (Col_1, Col_2, Col_3) select Col_1, Col_2, Col_3 from inserted go I ran the common script six times for each case -- three times cleaning SQL Server memory and three times without cleaning it -- and here are the results I received from SQL Profiler: The averages for CPU, reads, writes and duration were very close for all options.
Otherwise, if you are not sure which solution is best in a specific case, just test it as I have demonstrated.
A computed column is a virtual column that is not physically stored in the table, unless the column is marked PERSISTED.
The column is computed from an expression that uses other columns in the same table.
SQL statements running in triggers follow the same rules that standalone SQL statements do.
Specifically: How Triggers and Constraints Differ Both triggers and constraints can constrain data input, but they differ significantly. For example, a trigger can prevent a DML statement from inserting a values that were inserted into the column before the trigger was defined or while the trigger was disabled.
Constraints are easier to write and less error-prone than triggers that enforce the same rules.