How To Extract Substring In Sql

Friday, November 25th 2022. | Sample Excel

How To Extract Substring In Sql – Do you work with text data in SQL? We explain how to get values ​​from any point in a chain.

When you think of working with data in SQL, your first thought is a database full of numbers and your SQL code doing very sophisticated calculations. But the text is also provided! It is very common to find textual data in databases. Not only do you need to extract it, but you also need to manipulate it frequently. Functions that allow you to do this are called text functions.

How To Extract Substring In Sql

How To Extract Substring In Sql

For those who want to practice SQL functions, I recommend our Standard SQL Functions interactive course. It has 211 exercises and teaches you how to use common text, numeric, and date and time functions in SQL.

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🇧🇷 In this article, we have five real business examples that cover the main uses of this feature. Some of the examples may seem complicated if you’re not familiar with text functions, so make sure you have the standard SQL functions reference page or the SQL text functions overview handy.

Argument, you type a string literal or specify a column from which you want to extract the substring. Oh

Argument is an integer representing the numeric position of the character in the string at which the substring begins. Oh

The clue is in the function name itself. A substring is a string inside the main string. That’s why,

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In the above string, it is a substring that starts at position 1 and contains three characters

Now that we’ve covered the principles, I’ll show you several examples. Start, of course, with the easiest!

The function returns a substring of the desired string. You can write the string explicitly as an argument, like so:

How To Extract Substring In Sql

🇧🇷 The arguments say that the substring starts at the 9th character of the string and its length is 10 characters.

Sql Contains String

To show more interesting examples, I need some data. I present to you the table called Employees.

In the function Getting the first two letters of the email address means that the substring starts at the first character for a length of two characters. This returns the desired result:

, and the function still works. A good example is when you only want to display the year of the employment start date. You see, the column

, setting the start of the substring is sufficient. In this code, the substring starts at the fourth character. Since I omit the length argument, the length of the substring is the length from the fourth character to the end of the string. This is how I get the year easily, as you can see below:

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Get back to work with emails. According to company policy, the dot in place of an email address (ie the part before the ‘@’) is also the employee’s username for logging into all company applications. You must retrieve this username. See how:

The first two arguments are ones you’ve already seen. I want to extract a substring from the column

, and I want it to start from the first character of the string. But now, the substring length is different for each worker. How do I tell the function to return all characters before the ‘@’ symbol?

How To Extract Substring In Sql

In SQL Server or MySQL. Finds the specified character in the string and returns its numeric character position. So the length of the substring that is the employee’s username is the same

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The last example shows how to find an employee’s job title from the data. Working at Kooler, I know how jobs are created: first comes the employee’s seniority, then the department, then the job. For example, ‘Junior Sales Assistant’ means that the employee has junior seniority, is in sales and works as an assistant.

This is another example of omitting the length argument, although it’s a bit more complex. As usual, I first specify the string column –

In this case. After that I somehow need to find a substring consisting only of the last word of the job title.

🇧🇷 That’s a start; is three words long, including spaces. If I somehow subtracted the number of characters from the last word, I would have the length of the first two words, which would give me the start of the substring I want.

Substring In Sql Server

This is a bit tricky because different job titles have different lengths. The only thing that separates words is a space. So to get the length of the third word of the string I need to count the number of characters up to the white space but from the right.

The function reverses the string expression so that ‘Junior Sales Assistant’ becomes ‘tnatsissA selaS roinuJ’. The last word becomes the first; the word itself is also reversed, but that doesn’t matter here.

Finds the position of the space after the first word of the reversed string. This is equivalent to putting a space before the last word of the original (unreversed) string.

How To Extract Substring In Sql

Phew! Now if I subtract that number from the total length of the original string, I get the start of the substring, right?

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Well, not exactly! Using this difference, a substring is created that includes the last letter of the second word and the space before the last word. Why is that?

Calculates the space position, not the number of space characters. So I need to add 2 to get this result:

Now that I’ve covered some other features, you might want to take a look at some other text features that you might find useful.

There are other text functions, not just SUBSTRING(). You can find them (and much more!) in the Standard SQL Functions course.

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Although sure the course is for you? Here is a detailed description of what the course covers and how it can help you. In this article, we’ll briefly explain the SUBSTRING function and then focus on performance tips about it.

SQL Server offers many built-in functions that make complicated calculations easier for us. When we use these functions in the SELECT statement, the performance impacts are more acceptable. However, scalar functions can negatively affect query performance when used after WHERE clauses. The following rule is generally accepted as a performance practice to improve query performance.

The main idea behind this principle is that SQL Server cannot know the result of the function without executing the scalar function. Therefore, SQL Server must run the function individually for each row to find qualified data at runtime. Therefore, the data engine will read every index page or every row in the table, causing more I/O activity.

How To Extract Substring In Sql

The SUBSTRING function is one of the built-in functions and helps to extract character-specific data from text data in queries. This function is widely used in queries by database developers, so we will focus on the performance details of this function.

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This function can also be implemented with a SELECT statement that retrieves data from tables. The following query returns a specific subset of the PurchaseOrderNumber column values. In this use of the SUBSTRING function, it starts extracting values ​​from the second character of the column and continues to the seventh character. So it outputs five characters as specified in the length parameter of the function.

Overview of Substring Functions You can refer to this article to know more interesting facts about Substring() function.

In the following examples, we will use the AdventureWorks database and use the enlargement script (Create Enlarged AdventureWorks Tables) which helps to create a large amount of data. When we run this script, it will create the SalesOrderDetailEnlarged and SalesOrderHeaderEnlarged tables in the Sales schema.

The scalar computation operator performs a calculation and returns the value of that calculation. This operator is represented in execution plans by the following figure. The details property of this operator gives us detailed information about the executed function.

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Now let’s run the next query and dig into the details of the scalar operator property to calculate. The Defined Values ​​subattribute shows all the details about the scalar value function executed for the next query in the execution plan.

The LEFT function extracts the given character from the left side of the input string. Now let’s execute the following query that includes the LEFT function and examine the execution plan.

As we can clearly see, the LEFT function is an implementation of the SUBSTRING function. Of course, using the SUBSTRING function to calculate the LEFT function is a very logical approach. For example, the following two functions will return the same values.

How To Extract Substring In Sql

The RIGHT function does the opposite of the LEFT function and outputs the given character starting from the right of the input string. However, it does not use the SUBSTRING function in its calculations. Now let’s run the following query and examine the execution plan.

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This execution plan showed us that the feature of the RIGHT function is different from the LEFT function because the FunctionName property represents the correct value.

Now let’s remember and open up

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