12/4/2021 Android Room Auto Generated Primary Key
Mar 18, 2018 this tutorial will show you how to create a table in java db with a column named id as a primary key with auto increment. Skip navigation. How to Generate.
JDBCObject Oriented ProgrammingProgramming
While creating a table, in certain scenarios, we need values to column such as ID, to be generated/incremented automatically. Various databases support this feature in different ways.
In MySQL database you can declare a column auto increment using the following syntax.
MySQL query to create a table with auto-incremented column.
Example
Following JDBC program establishes a connection with MYSQL database and creates a query with an auto-incremented column.
OutputVerification
The DESCRIBE command in MYSQL gives the description of a table, you can verify the creation of the table with auto-incremented column using it, as shown below −
The
AUTO_INCREMENT attribute can be used to generate a unique identity for new rows:
Which returns:
No value was specified for the
AUTO_INCREMENT column, so MySQL assigned sequence numbers automatically. You can also explicitly assign 0 to the column to generate sequence numbers, unless the NO_AUTO_VALUE_ON_ZERO SQL mode is enabled. For example:
If the column is declared
NOT NULL , it is also possible to assign NULL to the column to generate sequence numbers. For example:
When you insert any other value into an
AUTO_INCREMENT column, the column is set to that value and the sequence is reset so that the next automatically generated value follows sequentially from the largest column value. For example:
Updating an existing
AUTO_INCREMENT column value in an InnoDB table does not reset the AUTO_INCREMENT sequence as it does for MyISAM and NDB tables.
You can retrieve the most recent automatically generated
AUTO_INCREMENT value with the LAST_INSERT_ID() SQL function or the mysql_insert_id() C API function. These functions are connection-specific, so their return values are not affected by another connection which is also performing inserts.
Use the smallest integer data type for the
AUTO_INCREMENT column that is large enough to hold the maximum sequence value you will need. When the column reaches the upper limit of the data type, the next attempt to generate a sequence number fails. Use the UNSIGNED attribute if possible to allow a greater range. For example, if you use TINYINT , the maximum permissible sequence number is 127. For TINYINT UNSIGNED , the maximum is 255. See Section 11.1.2, “Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT” for the ranges of all the integer types.
For a multiple-row insert,
LAST_INSERT_ID() and mysql_insert_id() actually return the AUTO_INCREMENT key from the first of the inserted rows. This enables multiple-row inserts to be reproduced correctly on other servers in a replication setup.
To start with an
AUTO_INCREMENT value other than 1, set that value with CREATE TABLE or ALTER TABLE , like this:
Android Room Auto Generated Primary Keyboard
For information about
AUTO_INCREMENT usage specific to InnoDB , see Section 14.9.1.4, “AUTO_INCREMENT Handling in InnoDB”.
Android Room Auto Generated Primary Key Of Florida
More information about
AUTO_INCREMENT is available here:
Android Room Auto Increment
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