SQL > SQL String Functions > CAST Function

The CAST function in SQL converts data from one data type to another. For example, we can use the CAST function to convert numeric data into character string data.


The syntax of the CAST function is as follows:

CAST (expression AS [data type])

where [data type] is a valid data type in the RDBMS you are working with.


We use the following table for our examples.

Table Student_Score

 Column Name  Data Type 
 StudentID  integer 
 First_Name  char(20) 
 Score  float 

This table contains the following rows:

Table Student_Score

 StudentID  First_Name  Score 
1Jenny 85.2 
2Bob 92.5 
3Alice 90 
4James 120.1 

Example 1

SELECT First_Name, CAST(Score AS Integer) Int_Score FROM Student_Score;


First_Name Int_Score
Jenny 85
Bob 92
Alice 90
James 120

In Example 1, we use the CAST function to convert the Score column from type FLOAT to INTEGER. When we do this, different RDMBS have different rules on how to handle the numbers after the decimal point. In the above example, the numbers after the decimal point are always truncated.

Example 2

SELECT First_Name, CAST(Score AS char(3)) Char_Score FROM Student_Score;


First_Name Char_Score
Jenny 85.
Bob 92.
Alice 90  
James 120

In Example 2, we use the CAST function to convert the SCORE column from type FLOAT to CHAR(3). When we do this, we only take the first three characters. So, if there are more than three characters, everything after the first three characters is discarded.

Next: SQL CONVERT Function

This page was last updated on June 19, 2023.

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