The core method for getting the last inserted ID in MySQL is to use the LAST_INSERT_ID() function, which returns the autoincrement ID generated by the last insertion in the current connection. 1. Get the ID directly after insertion: Call LAST_INSERT_ID() immediately after executing the INSERT statement, which is suitable for tables with self-increment primary keys; 2. Use in programming languages: For example, PDO extension of PHP calls the function through lastInsertId() and Python's mysql-connector encapsulated; 3. Performance when inserting multiple lines: Return the ID of the first insert record, not the last; 4. Notes include: connection isolation ensures that it is not affected by other connections, it is also applicable in transactions, does not support non-self-increment fields, and pay attention to the call order in stored procedures. Mastering these key points can safely and effectively obtain the last inserted ID.
The most common method to get the last inserted ID in MySQL is to use LAST_INSERT_ID() function. This function returns the autoincrement ID generated by the last INSERT operation in the current connection, and it is at the connection level and will not be affected by other connection operations.
Below are some specific scenarios and usage methods that you may use.
Basic usage: Get the ID directly after inserting
This is the most common usage. After you have executed an INSERT statement, immediately call LAST_INSERT_ID() to get the autoincrement primary key value of the record just inserted.
INSERT INTO users (name, email) VALUES ('Tom', 'tom@example.com'); SELECT LAST_INSERT_ID();
- This method is only applicable to tables with autoincrement primary keys (
AUTO_INCREMENT). - Regardless of whether you explicitly pass in the primary key value, as long as this insert triggers the generation of the self-increment field,
LAST_INSERT_ID()can get the correct value.
Used in programming languages: Take PHP and Python as examples
Most database drivers or ORMs encapsulate calls to LAST_INSERT_ID() , but understanding the underlying mechanism is still important.
PHP (PDO)
$pdo->exec("INSERT INTO users (name, email) VALUES ('Jerry', 'jerry@example.com')");
$lastId = $pdo->lastInsertId();Python (using mysql-connector)
cursor.execute("INSERT INTO users (name, email) VALUES (%s, %s)", ("Lucy", "lucy@example.com"))
print(cursor.lastrowid) Behind these encapsulations are actually calling MySQL's LAST_INSERT_ID() function.
Performance when inserting multiple lines
If you insert multiple pieces of data at once, LAST_INSERT_ID() returns the ID of the first inserted record.
INSERT INTO users (name, email) VALUES ('A', 'a@example.com'), ('B', 'b@example.com'), ('C', 'c@example.com'); SELECT LAST_INSERT_ID(); -- Returns the ID of the first record
For example, if the start ID is 100, then the three records are 100, 101, and 102, respectively, and LAST_INSERT_ID() returns 100.
This needs to be paid attention to in some batch import logic.
Notes and FAQs
- Connection isolation : Each connection has its own independent
LAST_INSERT_ID(), so you don't have to worry about being affected by insertion by other users. - It is also applicable in transactions : you can get the ID normally even if you perform insertions in a transaction.
- Non-self-increment fields are not supported : if the generated ID is not inserted through the self-increment field, such as a UUID or manually specifying the primary key, then this function will not be used.
- Don't use it randomly in stored procedures : Pay attention to the order when calling it in stored procedures, otherwise you may not get the correct value.
Basically that's it. By mastering the usage scenarios and limitations of LAST_INSERT_ID() , you can safely obtain the ID of the newly inserted record during development.
The above is the detailed content of how to get last inserted id in mysql. For more information, please follow other related articles on the PHP Chinese website!
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