The left function provides a way to retrieve the first n (number you specify) characters from a string. One often use of this function is to extract dates from a string, although SQL Server does provide some better functions for getting dates. In this article, we will learn how to use left with SQL Server.
The basic syntax of a LEFT is as follows:
SELECT LEFT(string, n);
For this, we will be using docker. This is recommended for more than just using SQL Server. To find how to install docker go here: https://docs.docker.com/engine/install/
Now create a file called
docker-compose.yml and add the following.
version: "3.9" services: db: image: "mcr.microsoft.com/mssql/server" ports: - 1433:1433 environment: SA_PASSWORD: "Your_password123" ACCEPT_EULA: "Y"
Open a terminal and go to the folder the file is located. Then run the following.
If you are looking for another good reference, you can check here: https://docs.docker.com/samples/aspnet-mssql-compose/.
Let's try this on a table. We can create an employee table and insert some rows.
CREATE TABLE employees ( first_name VARCHAR (50) NOT NULL, last_name VARCHAR (50) NOT NULL, ); insert into employees (first_name, last_name) values ('keith', 'holliday'), ('jon', 'doe'), ('jon', 'dane'), ('jane', 'done'), ('anna', 'smith');
Below is an example of extracting the first 3 characters from each of the employees last name. This could be use to construct a unique id or an email.
select left(last_name, 3) as LastName from employees e;