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✅ Basic Commands:
– `SELECT * FROM table_name;`
– `SELECT column1, column2 FROM table_name WHERE condition;`
– `SELECT * FROM table_name ORDER BY column_name ASC|DESC;`
– `SELECT column_name, COUNT(*) FROM table_name GROUP BY column_name;`
– `SELECT column_name, COUNT(*) FROM table_name GROUP BY column_name HAVING COUNT(*) > 5;`
– `SELECT * FROM table_name LIMIT 10;`
✅ Joins:
– `SELECT * FROM table1 INNER JOIN table2 ON table1.column = table2.column;`
– `SELECT * FROM table1 LEFT JOIN table2 ON table1.column = table2.column;`
– `SELECT * FROM table1 RIGHT JOIN table2 ON table1.column = table2.column;`
– `SELECT * FROM table1 FULL JOIN table2 ON table1.column = table2.column;`
✅ Aggregation:
– `SELECT COUNT(column_name) FROM table_name;`
– `SELECT SUM(column_name) FROM table_name;`
– `SELECT AVG(column_name) FROM table_name;`
– `SELECT MIN(column_name) FROM table_name;`
– `SELECT MAX(column_name) FROM table_name;`
✅ Subqueries & CTEs:
– `SELECT * FROM (SELECT * FROM table_name WHERE condition) AS subquery;`
– `WITH cte_name AS (SELECT * FROM table_name) SELECT * FROM cte_name;`
✅ Indexes:
– `CREATE INDEX index_name ON table_name (column_name);`
– `DROP INDEX index_name ON table_name;`
✅ Normalization:
- Ensure 1NF, 2NF, and 3NF to reduce redundancy and improve efficiency.
✅ Transactions:
– `BEGIN TRANSACTION;`
– `COMMIT;`
– `ROLLBACK;`
What Undercode Say
SQL is a powerful language for managing and manipulating relational databases. Mastering SQL commands like SELECT, JOIN, and `GROUP BY` is essential for data analysis and database management. Indexes and normalization are critical for optimizing database performance, while transactions ensure data integrity.
For Linux users, SQL commands can be executed in terminal using tools like `mysql` or psql. For example:
– `mysql -u username -p database_name` to connect to a MySQL database.
– `\dt` in PostgreSQL to list all tables.
Windows users can use tools like MySQL Workbench or SQL Server Management Studio (SSMS) for database management.
For further learning, check out these resources:
Practice these commands regularly to build confidence and efficiency in SQL. Whether you’re preparing for interviews or working on real-world projects, SQL is a must-have skill in the IT and data science fields.
Random Word: Serendipity
References:
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