Summary: in this tutorial, we will show you how to use MySQL CAST function to convert a value of any type into a value with a specified type.
Introduction to MySQL CAST function
The syntax of the MySQL CAST() function is as follows:
CAST(expression AS TYPE)
The CAST() function converts a value of any type into a value that has a specified type. The target type can be any one of the following types: BINARY, CHAR, DATE, DATETIME, TIME,DECIMAL, SIGNED, UNSIGNED.
The CAST() function is often used to return a value with a specified type for comparison in the WHERE, JOIN, and HAVING clauses.
Let’s take a look at some examples of using the CAST() function.
MySQL CAST function examples
In the following example, MySQL converts a string into an integer implicitly before doing calculation:
SELECT (1 + '1')/2;
To explicitly convert a string into an integer, you use the CAST() function as the following statement:
SELECT (1 + CAST('1' AS UNSIGNED))/2;
The following statement explicitly convert an integer into a string and concatenate the string with another string:
SELECT CONCAT('MySQL CAST example #',CAST(2 AS CHAR));
Let’s take a look at the orders table in the sample database.
See the following query:
SELECT orderNumber, requiredDate FROM orders WHERE requiredDate BETWEEN '2003-01-01' AND '2003-01-31';
The query selects orders whose required dates are in January 2003. The data type of the requireDate column is DATE therefore MySQL has to convert the literal strings: '2003-01-01' and '2003-01-31' into TIMESTAMP values before evaluating WHERE condition.
However, to be safe, you can use CAST() function to explicitly convert a string into a TIMESTAMP value as follows:
SELECT orderNumber, requiredDate FROM orders WHERE requiredDate BETWEEN CAST('2003-01-01' AS DATETIME) AND CAST('2003-01-31' AS DATETIME);
The following statement converts DOUBLE values into CHAR values and uses the results as the arguments of the CONCAT function:
SELECT productName, CONCAT('Prices(', CAST(buyprice AS CHAR), ',', CAST(msrp AS CHAR), ')') prices FROM products;
In this tutorial, you have learned how to use the MySQL CAST() function to convert a value with any type into a value with a specified type.
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