SQL: Removing Decimal Places Without Using ROUND
Many SQL users find themselves needing to remove decimal places from a number without resorting to the ROUND() function. This might be due to needing to truncate the value rather than round it, or perhaps ROUND() isn't available in your specific SQL dialect. This guide explores several effective methods to achieve this, focusing on clarity and SQL standard compliance.
Understanding the Problem
Before diving into solutions, let's clarify the difference between truncating and rounding. ROUND() rounds a number to the nearest whole number or specified decimal place. Truncating, on the other hand, simply removes the decimal portion, effectively chopping off any digits after the decimal point.
Methods for Removing Decimal Places
Here are several methods to remove decimal places without using ROUND(), catering to different SQL dialects:
Method 1: CAST or CONVERT to Integer
This is the most straightforward approach and generally works across various SQL databases. We simply change the data type of the numeric column to an integer type. The decimal portion is automatically dropped.
SELECT CAST(your_column AS INT) AS truncated_column
FROM your_table;
--Alternative using CONVERT (for some databases like SQL Server)
SELECT CONVERT(INT, your_column) AS truncated_column
FROM your_table;
Explanation: CAST (or CONVERT) explicitly converts the numeric value (your_column) to an integer (INT). Any fractional part is discarded during this conversion.
Method 2: Using FLOOR() Function
The FLOOR() function returns the largest integer less than or equal to the input value. This effectively truncates the number by removing the decimal portion. This is a more standard SQL function and usually supported across various database systems.
SELECT FLOOR(your_column) AS truncated_column
FROM your_table;
Explanation: FLOOR(3.7) would result in 3. FLOOR(-3.7) would result in -4.
Method 3: Using TRUNCATE() Function (MySQL, PostgreSQL, and others)
Some database systems, such as MySQL and PostgreSQL, provide a dedicated TRUNCATE() function specifically designed for this purpose.
SELECT TRUNCATE(your_column, 0) AS truncated_column
FROM your_table;
Explanation: The second argument 0 specifies that we want to truncate to zero decimal places.
Choosing the Right Method
The best method depends on your specific SQL database system. The CAST/CONVERT approach is highly portable, working across a broad range of systems. However, FLOOR() is a more widely recognized and standard SQL function. TRUNCATE() offers a more explicit name for this operation if supported by your database.
Remember to replace your_column and your_table with the actual names from your database. Always test your chosen method thoroughly to ensure it produces the expected results and handles negative numbers appropriately.
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