To set an auto-increment field in a certain table in the SQL Server database, the field type must be a numeric type, such as decimal, int, numeric, smallint, bigint, tinyint, etc. It should be noted that if the decimal and numeric types are set to auto-increment columns , The number of decimal places must be 0, otherwise the setting is unsuccessful.
The keyword syntax for setting auto-increment is: create table table name (field name field type identity(m,n)), the field type must be numeric and integer. m is the starting value of the auto-increment id, n is the step size, which means starting from m and increasing by n each time.
If neither value is specified, the default is (1,1), and the two values can be specified at the same time
by default, and only one parameter is not supported.
I don’t know if you have noticed: both m and n can be negative. If n is a negative number, id is decremented by 1 each time. Has anyone used the auto-decrement function of auto-increment columns?
The two most commonly used functions are auto-incremented:
The first one turns off auto-increment, manually inserts an id value, and then turns on auto-increment.
The syntax is as follows:
set identity_insert table name on;
insert into table name (column name 1, column name 2, column name 3, column name 4) values (data 1, data 2, data 3, data 4);
set identity_insert table name off;
The column name 1 is an auto-increasing column.
The second common function is to set the next value of the auto-increment column to the value you want
The syntax is as follows:
DBCC CHECKIDENT ('[data table name]', RESEED, [required value -1])
For example, if you want to set the value of the next auto-increment id to 10000, then
DBCC CHECKIDENT (table_name,RESEED, 9999).
When inserting data again, you will see that the value of the auto-increment id column is 10000.
Well, I will study here today. Through this article, have you learned a trick?