Category: DBMS

Database Management Systems

6 Functions to Get the Day, Month, and Year from a Date in SQL Server

Posted on by Ian

Transact-SQL includes a bunch of functions that help us work with dates and times. One of the more common tasks when working with dates is to extract the different parts of the date. For example, sometimes we only want the year, or the month. Other times we might want the day of the week. Either way, there are plenty of ways to do this in SQL Server.

In particular, the following functions allow you to return the day, month, and year from a date in SQL Server.

These functions are explained below.

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SQL Server DATEPART() vs DATENAME() – What’s the Difference?

Posted on by Ian

When working with dates in SQL Server, sometimes you might find yourself reaching for the DATEPART() function, only to realise that what you really need is the DATENAME() function. Then there may be other situations where DATEPART() is actually preferable to DATENAME().

So what’s the difference between the DATEPART() and DATENAME() functions?

Let’s find out.

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DATEPART() Examples in SQL Server

Posted on by Ian

In SQL Server, the T-SQL DATEPART() function returns an integer that represents the specified datepart of the specified date. For example, you can pass in 2021-01-07 and have SQL Server return only the year portion (2021).

You can also extract the time portion. For example, you can pass in 2018-06-02 08:24:14.3112042 and have SQL Server return only the hour portion (8).

Examples below.

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5 Ways to Get the Short Month Name from a Date in SQL Server

Posted on by Ian

Sometimes when working with SQL Server (or any other DBMS for that matter), you need to return the short name for a month. By this I mean the 3 letter abbreviation of a month. For example, you need “Dec” instead of “December”.

Here are four ways you can extract the shortened month name from a date in SQL Server.

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How to Fix the “datediff function resulted in an overflow” Error in SQL Server

Posted on by Ian

This article provides a solution to a problem you may occasionally encounter while using the DATEDIFF() function in SQL Server.

If you encounter the following error:

The datediff function resulted in an overflow. The number of dateparts separating two date/time instances is too large. Try to use datediff with a less precise datepart.

It’s because the return value is too large. The DATEDIFF() function returns its result as an int data type. The reason you got this message is that the return value is too big for the int data type. Fortunately there’s an easy way to fix this.

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4 Ways to Replace NULL with a Different Value in MySQL

Posted on by Ian

In MySQL, sometimes you don’t want NULL values to be returned as NULL. Sometimes you want NULL values to be returned with a different value, such as “N/A”, “Not Applicable”, “None”, or even the empty string “”.

Fortunately there are several ways to do this in MySQL.

Here are four:

  • The IFNULL() function
  • The COALESCE() function
  • The IF() function combined with the IS NULL (or IS NOT NULL) operator
  • The CASE expression combined with the IS NULL (or IS NOT NULL) operator

Examples of these options are below.

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How to Replace NULL with Another Value in SQL Server – ISNULL()

Posted on by Ian

When querying a SQL Server database, there may be times where you don’t want null values to be returned in your result set. And there may be times where you do want them returned. But there may also be times where you do want them returned, but as a different value.

That’s what the ISNULL() function is for.

ISNULL() is a T-SQL function that allows you to replace NULL with a specified value of your choice.

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MySQL Group_Concat() vs T-SQL String_Agg()

Posted on by Ian

One of the T-SQL functions introduced in SQL Server 2017 is the STRING_AGG() function. This is basically the equivalent of MySQL’s GROUP_CONCAT() function – it lets you return query results as a delimited list, rather than in rows.

But there are a few minor differences between the two functions.

This article explores some of the main syntax differences between these functions.

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The SQL Server Equivalent to GROUP_CONCAT()

Posted on by Ian

Before SQL Server 2017 came along, there wasn’t a T-SQL equivalent of the MySQL GROUP_CONCAT() function. This function allows you to return a result set as a comma-separated list, as opposed to listing each row as a separate row (as with a normal result set).

Prior to SQL Server 2017, if you wanted to put your result into a comma separated list, you’d need to find a workaround, perhaps using a combination of STUFF() and FOR XML PATH().

However, T-SQL now has the STRING_AGG() function which is available from SQL Server 2017. This function does pretty much the same thing as MySQL’s GROUP_CONCAT() function (with some minor differences).

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