267 lines
3.4 KiB
Markdown
267 lines
3.4 KiB
Markdown
# Comprehensive SQL Cheat Sheet
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## Table of Contents
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1. [Database Basics](#database-basics)
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2. [SQL Syntax](#sql-syntax)
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3. [Data Types](#data-types)
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4. [Table Operations](#table-operations)
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5. [Querying Data](#querying-data)
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6. [Filtering Data](#filtering-data)
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7. [Joins](#joins)
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8. [Aggregate Functions](#aggregate-functions)
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9. [Group By](#group-by)
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10. [Subqueries](#subqueries)
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11. [Transactions](#transactions)
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12. [Indexes](#indexes)
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13. [Views](#views)
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## Database Basics
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### Creating a Database
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```sql
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CREATE DATABASE dbname;
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```
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### Using a Database
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```sql
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USE dbname;
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```
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### Deleting a Database
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```sql
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DROP DATABASE dbname;
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```
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## SQL Syntax
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### SELECT Statement
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```sql
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SELECT column1, column2 FROM table_name;
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```
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### WHERE Clause
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```sql
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SELECT * FROM table_name WHERE condition;
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```
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### ORDER BY Clause
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```sql
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SELECT * FROM table_name ORDER BY column1 ASC, column2 DESC;
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```
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### LIMIT Clause
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```sql
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SELECT * FROM table_name LIMIT 10;
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```
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## Data Types
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### Numeric Types
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```sql
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INT, FLOAT, DOUBLE, DECIMAL
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```
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### Character Types
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```sql
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CHAR, VARCHAR, TEXT
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```
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### Date and Time Types
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```sql
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DATE, TIME, DATETIME
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```
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## Table Operations
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### Creating a Table
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```sql
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CREATE TABLE table_name (
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column1 datatype,
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column2 datatype,
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...
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);
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```
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### Altering a Table
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```sql
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ALTER TABLE table_name
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ADD column_name datatype;
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```
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### Dropping a Table
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```sql
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DROP TABLE table_name;
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```
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## Querying Data
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### Basic SELECT
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```sql
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SELECT * FROM table_name;
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```
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### Aliasing Columns
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```sql
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SELECT column1 AS alias1, column2 AS alias2 FROM table_name;
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```
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## Filtering Data
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### WHERE Clause
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```sql
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SELECT * FROM table_name WHERE condition;
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```
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### AND, OR, NOT
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```sql
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SELECT * FROM table_name WHERE condition1 AND condition2;
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```
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### IN Clause
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```sql
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SELECT * FROM table_name WHERE column_name IN (value1, value2);
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```
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## Joins
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### INNER JOIN
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```sql
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SELECT * FROM table1 INNER JOIN table2 ON table1.column = table2.column;
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```
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### LEFT JOIN
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```sql
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SELECT * FROM table1 LEFT JOIN table2 ON table1.column = table2.column;
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```
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### RIGHT JOIN
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```sql
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SELECT * FROM table1 RIGHT JOIN table2 ON table1.column = table2.column;
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```
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## Aggregate Functions
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### COUNT
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```sql
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SELECT COUNT(column) FROM table_name;
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```
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### SUM
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```sql
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SELECT SUM(column) FROM table_name;
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```
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### AVG
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```sql
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SELECT AVG(column) FROM table_name;
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```
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### MIN and MAX
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```sql
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SELECT MIN(column), MAX(column) FROM table_name;
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```
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## Group By
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```sql
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SELECT column1, COUNT(column2) FROM table_name GROUP BY column1;
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```
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## Subqueries
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### Single-Row Subquery
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```sql
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SELECT column1 FROM table_name WHERE column2 = (SELECT column2 FROM another_table WHERE condition);
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```
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### Multi-Row Subquery
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```sql
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SELECT column1 FROM table_name WHERE column2 IN (SELECT column2 FROM another_table WHERE condition);
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```
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## Transactions
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### Begin Transaction
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```sql
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BEGIN;
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```
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### Commit Transaction
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```sql
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COMMIT;
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```
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### Rollback Transaction
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```sql
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ROLLBACK;
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```
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## Indexes
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### Creating an Index
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```sql
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CREATE INDEX index_name ON table_name (column1, column2);
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```
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### Dropping an Index
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```sql
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DROP INDEX index_name;
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```
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## Views
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### Creating a View
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```sql
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CREATE VIEW view_name AS
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SELECT column1, column2 FROM table_name WHERE condition;
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```
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### Updating a View
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```sql
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CREATE OR REPLACE VIEW view_name AS
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SELECT new_column1, new_column2 FROM table_name WHERE condition;
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```
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### Dropping a View
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```sql
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DROP VIEW view_name;
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```
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