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Merge pull request #442 from michaelmjhhhh/michaelmjhhhh-update-mysql-cheatsheet

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Add essential sections to MySQL: Alter, Indexes, and Transactions
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Julien Le Coupanec
2026-04-12 19:26:10 +02:00
committed by GitHub
parent 925eff9d91 6326628901
commit 38f406dc19
1 changed files with 30 additions and 0 deletions
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databases/mysql.sh
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@@ -82,3 +82,33 @@ SELECT User, Host FROM mysql.user; # List all current MySQL users
SET GLOBAL general_log = 'ON'; # Enable query logging SET GLOBAL general_log = 'ON'; # Enable query logging
SHOW FULL PROCESSLIST; # Show the last queries executed in MySQL SHOW FULL PROCESSLIST; # Show the last queries executed in MySQL
# *****************************************************************************
# Altering Table Structure
# *****************************************************************************
ALTER TABLE table_name ADD COLUMN column_name datatype; # Add a new column to an existing table
ALTER TABLE table_name MODIFY COLUMN column_name datatype; # Change the data type of a column
ALTER TABLE table_name RENAME COLUMN old_name TO new_name; # Rename a column (MySQL 8.0+)
ALTER TABLE table_name DROP COLUMN column_name; # Remove a column from a table
ALTER TABLE old_table_name RENAME TO new_table_name; # Rename an entire table
# *****************************************************************************
# Indexes (Performance Tuning)
# *****************************************************************************
CREATE INDEX idx_name ON table_name (column_name); # Create a standard index to speed up queries
CREATE UNIQUE INDEX idx_name ON table_name (column_name); # Create a unique index (no duplicate values)
SHOW INDEX FROM table_name; # List all indexes on a specific table
DROP INDEX idx_name ON table_name; # Remove an index from a table
EXPLAIN SELECT * FROM table_name WHERE condition; # Analyze how MySQL executes a query (Check index usage)
# *****************************************************************************
# Transactions (Data Integrity)
# *****************************************************************************
START TRANSACTION; # Begin a new transaction
COMMIT; # Save all changes made during the transaction
ROLLBACK; # Undo all changes if an error occurs before commit
SET AUTOCOMMIT = 0; # Disable automatic commits for the current session
SET AUTOCOMMIT = 1; # Re-enable automatic commits after finishing manual transactions