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1. Why Do Data Types Matter?
SQL data types define the kinds of values a column can store and determine how the database validates, stores, and processes those values.
Choosing the right data type helps prevent errors, improves performance, and saves storage space.
2. Common SQL Data Types
| Type | Description | Example |
|---|---|---|
TEXT | String of characters, unlimited length | 'Laura Adams' |
VARCHAR | Variable-length string with a maximum length limit | 'John Doe' |
INT | Whole numbers (integers) | 42 |
REAL | Decimal (floating-point) numbers (also called FLOAT) | 89.5 |
DATE | Calendar dates in YYYY-MM-DD format by default | '2023-03-05' |
BOOLEAN | Logical values (TRUE/FALSE, sometimes 1/0) | TRUE, FALSE |
These are used when defining table columns.
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3. Scenario: Client Table Design
Imagine you're creating a table of registered clients. You might choose:
id→INT(each client has a unique number)name→TEXTemail→TEXTsignup_date→DATE
Selecting the right types keeps data clean, consistent, and easy to query.
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4. Bad Type Choices = Trouble
If you store a date as TEXT:
- It's harder to filter by range
- You can't sort chronologically
- It's prone to format inconsistencies
If you store numbers as TEXT, you can't perform calculations.
💡 Always match the data to the most suitable type.
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5. Summary: Design for Accuracy
✔ Use TEXT for names, descriptions, categories
✔ Use INT for counts, IDs, ages
✔ Use REAL for scores, prices
✔ Use DATE for timestamps
✔ Use BOOLEAN for yes/no logic
Choosing correctly makes queries faster and data cleaner.
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