SQL has a wide variety of string functions, each of them useful for particular cases. In this post, we will explore them so you know how to use them for performance optimization in SQL.
String Functions: Know More to Improve Performance of SQL Query
Each of the string functions we will cover is explained below in simple terms:
DATALENGTH: This is a SQL function that fetches the length of the data mentioned in the command.
DIFFERENCE: It makes a comparison between 2 Soundex values. Soundex is a string format that turns alphanumeric strings into codes that consist of 4 characters. This conversion depends on the sound the string makes in English.
Coming back to the DIFFERENCE function, it fetches an integer between one and four going from weakest to strongest. These integers show the similarity between the different words in the string. This could be helpful if you want to improve the performance of SQL queries.
ASCII: ASCII is short for the American Standard Code for Information Interchange. The goal of this function, therefore, is to present the ASCII value of the first character that is present.
CHAR: This function works in reverse as compared to the previous string function (ASCII). That’s because it fetches the value of the character on the basis of n ASCII values.
CHARINDEX: This is a SQL string function that brings back the index for the mentioned character that finds itself in a particular string.
CONCAT: This is the concatenate string function that combines 2 strings to form a single string.
FORMAT: As the name suggests, this function has something to do with the format of the specified string in a field. Specifically, it presents a value in a format that is also mentioned in the command.
LEFT: This SQL function picks out a number of characters from a pre-defined string. The number of characters that it will extract is also mentioned in the command.
LOWER: It works on the case of the string, changing it from upper case to lower case (if applicable; otherwise it returns the string in lower case).
LTRIM: It works to ‘trim’ the spaces on the left of the string mentioned in the query, helping with optimization in SQL. It will remove only the spaces on the left, however, before returning the string.
NCHAR: It represents string information of a specific size, where n stands for size in byte-pairs. Its value has to fall within the range of 1-4000. The final size equals twice the value of n bytes.
PATINDEX: It is a function that brings back the signs of a pattern if there is any present in the mentioned string. If there is a pattern, it will return that, otherwise it will fetch 0.
QUOTENAME: It brings a Unicode string upon execution. However, whatever it fetches contains delimiters to ensure validity in SQL Server. If you add brackets, the result will have those brackets.
REPLACE: Its task is to change the string the user wants to replace with the string they mention in the query. Such functions can be useful for smaller tables when you have to improve performance of SQL query.
REVERSE: It presents the string in the command in reverse order. For instance, “rage” will become “egar”.
RIGHT: This string function is similar to the LEFT function. The only difference is that it takes out the number of characters as the user specifies from the right instead of the left.
RTRIM: As its name suggests, it works in a manner similar to LTRIM. However, it trims trailing spaces, i.e., the spaces to the right of the string- all of them.
SOUNDEX: The purpose of this string function is to analyze how similar or like-sounding two strings are.
STR: STR is short for string, as you might have guessed. Its task is to change numerical values into string types.
STUFF: It ‘stuffs’ any kind of string segment after it removes a part of the string specified by the user.
SUBSTRING: This function takes out some characters from the user-specified string.
TRIM: This is just like the LTRIM and RTRIM functions, except that it does both their work in one go. Rather than use LTRIM and RTRIM separately, you can simply go for TRIM when you have to remove all the unnecessary spaces from both the left and the right (leading and trailing spaces).
UPPER: It works opposite to LOWER as it changes the string to uppercase.
LEN: It is short for length and its use is fetching string length without including trailing spaces. If you want to improve performance of SQL query and know the number of spaces, try using data length instead.
SPACE: This fetches a string that contains the number of spaces according to the value that the user specifies.
These are the most well-known SQL String functions that help in various situations including optimization in SQL.
The more you work with SQL, the more familiar you will get with all of these as well as other functions. Although examples around the internet generally cover hardcoded values, you can use them with variables since the data will originate from various sources.