Category Archives: SQL Functions

SUBSTRING function is used in sql to select part of text string in text. This function belongs to the group of text functions – string functions. I created a big summary of T-SQL text functions – you can find it here. SQL SUBSTRING Syntax SELECT SUBSTRING(text, <start position of the text character>, <the number of… Read More »

SQL COUNT function belongs to Aggregate functions and it is one of the most easy-to-use and also most used functions of SQL. It enables user to count rows in certain column or rows in whole table. NULL records are missed out if we count number of records above certain column using sql COUNT. SQL COUNT… Read More »

REPLACE function is used to replace text string or its parts. It belongs to the category of string functions. I created big overview of T-SQL text functions some time ago. SQL REPLACE Syntax (3 arguments) SELECT REPLACE(<Column with text in which we replace part of the text>, <The string we want to replace>, <New string>)… Read More »

ISNULL and COALESCE are functions used for work with null values (NULL). Both functions return first value out of previously defined entry parameters. There are also some differences between both functions. ISNULL Syntax: SELECT ISNULL(<Column>, <Column Replacement – other column or logic>) FROM dbo.Table  COALESCE Syntax: SELECT COALESCE(<Column>, <Column Replacement – other column or logic… Read More »

T-SQL is not a language designed primarily to do something big with text strings or manipulate with them. That is the reason why we will not find many text-related built-in functions. But we will definitely find use for those that are there. Let’s take a look at SQL String Functions. Text Concatenation (Combining) – CONCAT… Read More »

SQL aggregate functions AVG, COUNT, MAX, MIN, SUM are used the most. That is because we often need to add, make average or find the highest or lowest value. It is mandatory to use GROUP BY clause anytime when we use aggregate function.  (except for operations over windows using OVER()) List of SQL Server Aggregate… Read More »

SQL ranking functions enable us to rank records in the table based on values of a field or multiple fields. Clause OVER() is mandatory for the ranking functions. Ranking functions belongs to the group of Window functions. Aggregate functions and Offset functions (for paging) also belong to this group. List of Ranking Functions ROW_NUMBER ()… Read More »