SQL Data Type
Q1. What is a Data Type in SQL and why is it important?
A data type in SQL defines the kind of data that can be stored in a column of a table. It tells the database how to store, validate, and process the values of that column. Every column must have a data type because the database engine needs to know whether the data is numeric, textual, date-based, or boolean.
Data types are important because they:
Data types are important because they:
- Maintain data accuracy by preventing invalid entries
- Improve performance by optimizing storage and query execution
- Save memory space by using appropriate formats
- Help SQL perform correct operations like calculations or comparisons
Q2. Explain different categories of SQL data types.
SQL data types are broadly categorized into:
1. Numeric Data Types
Used to store numbers such as counts, prices, and measurements.
Examples include INT, DECIMAL, FLOAT, and BIGINT.
2. String (Text) Data Types
Used to store characters, names, and descriptions.
Common examples are CHAR, VARCHAR, and TEXT.
3. Date and Time Data Types
Used to store dates, time, or both.
Examples include DATE, TIME, DATETIME, and YEAR.
4. Boolean and Miscellaneous Data Types
Used for true/false values, fixed choices, or binary data.
Examples include BOOLEAN, ENUM, and BLOB.
Each category serves a specific purpose and must be chosen carefully based on real-world data requirements.
1. Numeric Data Types
Used to store numbers such as counts, prices, and measurements.
Examples include INT, DECIMAL, FLOAT, and BIGINT.
2. String (Text) Data Types
Used to store characters, names, and descriptions.
Common examples are CHAR, VARCHAR, and TEXT.
3. Date and Time Data Types
Used to store dates, time, or both.
Examples include DATE, TIME, DATETIME, and YEAR.
4. Boolean and Miscellaneous Data Types
Used for true/false values, fixed choices, or binary data.
Examples include BOOLEAN, ENUM, and BLOB.
Each category serves a specific purpose and must be chosen carefully based on real-world data requirements.
Q3. What is the difference between CHAR and VARCHAR?
CHAR is a fixed-length data type, while VARCHAR is a variable-length data type.
For example:
- CHAR(n) always reserves n characters, even if the stored value is shorter.
- VARCHAR(n) only uses as much space as needed for the actual text.
For example:
- CHAR(5) storing 'YES' still uses 5 characters.
- VARCHAR(5) storing 'YES' uses only 3 characters.
Q4. When should DECIMAL be used instead of FLOAT?
DECIMAL should be used when exact precision is required, such as storing prices, salaries, or financial data.
FLOAT and DOUBLE store approximate values and may cause rounding errors.
Example:
FLOAT and DOUBLE store approximate values and may cause rounding errors.
Example:
- DECIMAL(8,2) - accurate monetary values like 1999.99
- FLOAT - scientific or approximate calculations