Locking Tables with Transaction in MySQL

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If you've ever been in the wild west of database management, you probably know a thing or two about the importance of locking the saloon doors (or, in our case, tables). At any given moment, a bandit (another user or process) may try to update the same table you're working on, leading to potential data conflicts or worse, data corruption.

Transactions

Before we delve into locking tables, let's revisit the concept of transactions. A transaction in a database is like a little story. Each story has a beginning, a middle, and an end. In terms of database operations, it's a sequence of operations that are treated as a single unit. Either all operations succeed, or none at all. That's the essence of a transaction, providing an all-or-nothing approach to handle data modifications.

Locking Tables

Now, imagine two people trying to tell their stories (transactions) at the same time, and their stories involve the same table. Chaos, right? That's where locking tables comes into the picture. It's like granting an exclusive stage to one transaction at a time, while others wait in the queue.

In MySQL, you can lock tables with a transaction using the LOCK TABLES statement. However, do note that upon executing this statement, any existing transaction is implicitly committed. Here's a simple demonstration:

START TRANSACTION;

LOCK TABLES employees WRITE;

SELECT COUNT(*) FROM employees;  -- This will return the total number of employees.

UPDATE employees SET salary = salary * 1.05;  -- Give all employees a 5% raise.

COMMIT;

UNLOCK TABLES;

In the above example, we start a transaction, lock the employees table for write operations, perform a SELECT and an UPDATE operation, commit the changes, and then unlock the tables.

It's important to remember to unlock the tables once you're done with the transaction. Not doing so is like forgetting to unlock the saloon doors after you're done with your drink. Nobody else can get in, and that's not really fair, is it?

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