SQL
SQL DataTypes
SQL data types define the type of data that can be stored in a table's columns. They help ensure data integrity and optimize storage. Here is an overview of common SQL data types:
Numeric Data Types
| DataType | Description |
|---|---|
| INTEGER | Stores whole numbers. |
| SMALLINT | Stores smaller range of whole numbers. |
| BIGINT | Stores larger range of whole numbers. |
| DECIMAL | Stores fixed-point numbers. |
| NUMERIC | Similar to DECIMAL. |
| FLOAT | Stores floating-point numbers with approximate precision. |
| REAL | Stores floating-point numbers with less precision than FLOAT. |
| DOUBLE | Stores double precision floating-point numbers. |
Character String Data Types
| DataType | Description |
|---|---|
| CHAR | Fixed-length character string. |
| VARCHAR | Variable-length character string. |
| TEXT | Variable-length character string with unlimited length. |
Date and Time Data Types
| DataType | Description |
|---|---|
| DATE | Stores date values. |
| TIME | Stores time values. |
| TIMESTAMP | Stores date and time values. |
| DATETIME | Stores date and time values (often used interchangeably with TIMESTAMP in some RDBMS). |
| YEAR | Stores year values. |
General Tips!
- Use Proper Indexing: Index frequently queried columns to improve query performance, but avoid over-indexing as it can slow down write operations.
- Write Efficient Queries: Optimize your queries by selecting only the necessary columns, avoiding SELECT *, and using joins wisely.
- Normalize Your Data: Organize your database into normalized tables to reduce redundancy and improve data integrity.
- Use Transactions: Ensure data consistency and integrity by wrapping multiple related operations in transactions, especially in multi-step processes.
- Understand and Use SQL Functions: Leverage built-in SQL functions for data manipulation and retrieval, such as aggregate functions (SUM, COUNT) and string functions (CONCAT, SUBSTRING).