How to convert integer to decimal in SQL Server query?

Grasping data type precedence

SQL Server relies heavily on data type precedence when performing arithmetic. It directly impacts your conversion from integer to decimal in an expression. Check this out:

SELECT height * 1.0 AS DecimalHeight FROM your_table;
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Multiplying by 1.0 (our "decimal fairy dust"✨) implicitly converts height to a decimal. Why? Because in the realm of SQL Server, floating point 1.0 has a higher precedence than an integer.

Precision control and rounding

Worried about maintaining precision post division? Sprinkle in some ROUND. It's like the "barber" of SQL, it trims off the unruly ends of numbers!

SELECT ROUND(height / CAST(10 AS FLOAT), 2) AS DecimalHeightRounded FROM your_table;
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In this scenario, the ROUND function comes in clutch, defining the number of decimal places to make sure everything is neat and rounded to the nearest hundredth.

Dealing with variables

Variables sneaking up on you? Use the CAST function to shoo them into line:

DECLARE @IntegerValue INT = 12345;
SELECT CAST(@IntegerValue AS DECIMAL(10, 2)) AS DecimalValue;
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Just like that, we've converted the integer variable @IntegerValue to a decimal with the magic numbers we want: precision and scale.

Customizing scale and precision

Playing with data types

When turning integers to decimals, we must choose a DECIMAL data type that fits our data's scale and precision just right:

-- Potential "money-making" conversion
SELECT CAST(Price AS DECIMAL(19, 4)) FROM Products;
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Preventing scale alterations

Imagine division as a "naughty child". It can alter the scale during operations:

SELECT height / 10.0 AS DecimalHeight
FROM your_table;
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Adding a decimal point (.) in the operand is like adding a "supervisor"(.) to keep division in check!

Precision and scale customization

Feeling the "control freak" vibe? Use CONVERT to dictate the precision and scale:

SELECT CONVERT(DECIMAL(10, 6), SomeLargeInteger) FROM BigNumbers;
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For those big numbers where standard precision might be too tight, this comes in handy.

Precision pitfalls and error handling

Defending against precision loss

Operations running rampant and causing precision loss? Always test your operations with a variety of values:

Going granular with floats

Need granular precision? Try a float for operations that need double the precision:

SELECT height / CAST(10 AS FLOAT) AS DecimalHeightWithDoublePrecision FROM your_table;
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Edge case protection

Ever heard of the "SQL Shield"⚔️? That's what we'll call our error handling for edge cases. Defend against underflow, overflow, and the taboo division by zero.