Mysql implements functions like nextval in oracle _ MySQL

Implementation of functions similar to nextval in oracle in mysql

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Implement nextval functions in mysql similar to those in oracle

We know that sequence is not supported in mysql. Generally, this field is auto-incrementing by the time the table is created.

For example, create table table_name (id int auto_increment primary key ,...);

Or alter table table_ame add id int auto_increment primary key // the field must be set to primary key.

Or reset the starting value of the auto-increment field. alter table table_name AUTO_INCREMENT = n

However, sequence_name.nextval is often used in oracle, or select sequence_name.value from dual in the program. if our development framework must support both oracle and mysql. We generally propose sequence. If a similar function is provided in mysql, it is more convenient to propose it. This is an application scenario. The following describes how to implement a nextval function in mysql.

1. create a table first

SQL code

Create table 'sys _ sequence '(

'Name' varchar (50) not null,

'Current _ value' int (11) not null default '0 ',

'Credentials' int (11) not null default '1 ',

Primary key ('name ')

)

2. create a function

SQL code

DELIMITER $

Drop function if exists 'currval' $

Create definer = 'root' @ '%' FUNCTION 'currval' (seq_name VARCHAR (50) returns int (11)

BEGIN

Declare value integer;

Set value = 0;

SELECT current_value INTO VALUE

FROM sys_sequence

Where name = seq_name;

Return value;

END $

DELIMITER;

Create definer = 'root' @ '%' FUNCTION 'nextval' (seq_name varchar (50) RETURNS int (11)

BEGIN

UPDATE sys_sequence

SET CURRENT_VALUE = CURRENT_VALUE + INCREMENT

Where name = seq_name;

Return currval (seq_name );

END

Create definer = 'root' @ '%' FUNCTION 'setval '(seq_name varchar (50), value integer) RETURNS int (11)

BEGIN

Update sys_sequence

Set current_value = value

Where name = seq_name;

Return currval (seq_name );

END

?

Test select nextval ('name.

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