mysql-best-practices

-- Appropriate data type selection
CREATE TABLE products (
    product_id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
    sku VARCHAR(50) NOT NULL,
    name VARCHAR(255) NOT NULL,
    description TEXT,
    price DECIMAL(10, 2) NOT NULL,
    quantity SMALLINT UNSIGNED NOT NULL DEFAULT 0,
    weight DECIMAL(8, 3),
    is_active TINYINT(1) NOT NULL DEFAULT 1,
    created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
    UNIQUE KEY uk_sku (sku)
) ENGINE=InnoDB;

-- UUID storage optimization
CREATE TABLE distributed_events (
    event_id BINARY(16) PRIMARY KEY,
    event_type VARCHAR(50) NOT NULL,
    payload JSON,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);
 
-- Insert with UUID
INSERT INTO distributed_events (event_id, event_type, payload)
VALUES (UUID_TO_BIN(UUID()), 'user_signup', '{"user_id": 123}');
 
-- Query with UUID
SELECT * FROM distributed_events
WHERE event_id = UUID_TO_BIN('550e8400-e29b-41d4-a716-446655440000');

-- Composite index for common query patterns
CREATE INDEX idx_orders_customer_date ON orders(customer_id, order_date);
 
-- Covering index
CREATE INDEX idx_orders_covering ON orders(customer_id, order_date, status, total_amount);
 
-- Fulltext index for search
ALTER TABLE products ADD FULLTEXT INDEX ft_name_desc (name, description);
 
-- Search using fulltext
SELECT * FROM products
WHERE MATCH(name, description) AGAINST('wireless bluetooth' IN NATURAL LANGUAGE MODE);

-- Check index usage
SELECT
    table_schema, table_name, index_name,
    seq_in_index, column_name, cardinality
FROM information_schema.STATISTICS
WHERE table_schema = 'your_database'
ORDER BY table_name, index_name, seq_in_index;

EXPLAIN FORMAT=JSON
SELECT c.name, COUNT(o.order_id) AS order_count
FROM customers c
LEFT JOIN orders o ON c.customer_id = o.customer_id
WHERE c.created_at > '2024-01-01'
GROUP BY c.customer_id;

-- Efficient pagination
SELECT order_id, order_date, total_amount
FROM orders
WHERE customer_id = ?
ORDER BY order_date DESC
LIMIT 20 OFFSET 0;
 
-- Keyset pagination (more efficient for large offsets)
SELECT order_id, order_date, total_amount
FROM orders
WHERE customer_id = ?
    AND (order_date, order_id) < (?, ?)
ORDER BY order_date DESC, order_id DESC
LIMIT 20;

-- Avoid: Function on indexed column
SELECT * FROM orders WHERE YEAR(order_date) = 2024;
 
-- Preferred: Range comparison
SELECT * FROM orders
WHERE order_date >= '2024-01-01' AND order_date < '2025-01-01';
 
-- Avoid: Implicit type conversion
SELECT * FROM users WHERE user_id = '123';  -- user_id is INT
 
-- Preferred: Proper types
SELECT * FROM users WHERE user_id = 123;
 
-- Avoid: LIKE with leading wildcard
SELECT * FROM products WHERE name LIKE '%phone%';
 
-- Preferred: Fulltext search for text matching
SELECT * FROM products WHERE MATCH(name) AGAINST('phone');

CREATE TABLE events (
    event_id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
    event_type VARCHAR(50) NOT NULL,
    payload JSON NOT NULL,
    -- Generated column for indexing
    user_id INT UNSIGNED AS (payload->>'$.user_id') STORED,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    INDEX idx_user_id (user_id)
);
 
-- Query JSON data
SELECT event_id, event_type,
       JSON_EXTRACT(payload, '$.action') AS action
FROM events
WHERE JSON_EXTRACT(payload, '$.user_id') = 123;
 
-- Or using -> operator
SELECT * FROM events WHERE payload->'$.user_id' = 123;

-- Transaction with error handling
START TRANSACTION;
 
UPDATE accounts SET balance = balance - 100 WHERE account_id = 1;
UPDATE accounts SET balance = balance + 100 WHERE account_id = 2;
 
-- Check for errors and commit or rollback
COMMIT;
 
-- Set isolation level
SET TRANSACTION ISOLATION LEVEL READ COMMITTED;

-- Check replication status
SHOW SLAVE STATUS\G
 
-- Check replication lag
SELECT TIMESTAMPDIFF(SECOND,
    MAX(LAST_APPLIED_TRANSACTION_END_APPLY_TIMESTAMP),
    NOW()) AS lag_seconds
FROM performance_schema.replication_applier_status_by_worker;

-- Create user with limited privileges
CREATE USER 'app_user'@'%' IDENTIFIED BY 'secure_password';
GRANT SELECT, INSERT, UPDATE, DELETE ON mydb.* TO 'app_user'@'%';
FLUSH PRIVILEGES;
 
-- Require SSL
ALTER USER 'app_user'@'%' REQUIRE SSL;
 
-- View user privileges
SHOW GRANTS FOR 'app_user'@'%';

-- Analyze tables for optimizer statistics
ANALYZE TABLE orders, customers, products;
 
-- Optimize tables (reclaim space, defragment)
OPTIMIZE TABLE orders;
 
-- Check table integrity
CHECK TABLE orders;

-- Find slow queries
SELECT * FROM mysql.slow_log ORDER BY query_time DESC LIMIT 10;
 
-- Current process list
SHOW FULL PROCESSLIST;
 
-- InnoDB status
SHOW ENGINE INNODB STATUS;
 
-- Table sizes
SELECT
    table_name,
    ROUND(data_length / 1024 / 1024, 2) AS data_mb,
    ROUND(index_length / 1024 / 1024, 2) AS index_mb,
    table_rows
FROM information_schema.TABLES
WHERE table_schema = 'your_database'
ORDER BY data_length DESC;

# my.cnf recommended settings
 
[mysqld]
# InnoDB settings
innodb_buffer_pool_size = 70%_of_RAM
innodb_log_file_size = 256M
innodb_flush_log_at_trx_commit = 1
innodb_flush_method = O_DIRECT
 
# Connection settings
max_connections = 500
wait_timeout = 300
interactive_timeout = 300
 
# Query cache (disabled in MySQL 8.0+)
query_cache_type = 0
 
# Slow query log
slow_query_log = 1
slow_query_log_file = /var/log/mysql/slow.log
long_query_time = 2