When working with SQL, it is important to know the data type of a variable. The data type determines the kind of values that can be stored in a column or variable.
It also affects how the data is stored and processed. In this tutorial, we will explore different ways to find the data type of a variable in SQL.
Using the DESCRIBE Statement
The DESCRIBE statement is commonly used to retrieve information about a table’s structure, including the data types of its columns. Let’s say we have a table called “customers” with columns like “id”, “name”, and “age”. To find the data type of a specific column, you can use the following syntax:
This will display information about all columns in the “customers” table, including their names, data types, and other attributes.
Using the SQL Data Type Functions
In addition to using the DESCRIBE statement, you can also use SQL built-in functions to determine the data type of a variable or expression.
The typeof() Function
The typeof() function returns the name of the data type for a specific expression. For example:
This will return ‘integer’ as 42 is an integer value.
The DATATYPE() Function
The DATATYPE() function returns a string representing the data type of an expression. For example:
SELECT DATATYPE('John Doe');
This will return ‘varchar’ as ‘John Doe’ is a character string.
Querying the Information Schema
The INFORMATION_SCHEMA is a special schema that provides information about all other schemas and tables in a database. By querying the INFORMATION_SCHEMA, you can find detailed information about the data types of columns in a table.
To find the data type of a specific column, you can use the following query:
SELECT DATA_TYPE FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = 'customers' AND COLUMN_NAME = 'name';
This will return the data type of the ‘name’ column in the ‘customers’ table.
Knowing the data type of a variable in SQL is essential for proper data manipulation and querying. You can use various methods such as the DESCRIBE statement, SQL data type functions like typeof() and DATATYPE(), and querying the INFORMATION_SCHEMA to find the data type of a variable. By understanding and utilizing these techniques, you can effectively work with different data types in your SQL queries.