What I have here today is a article for beginners. It will be full of sql query examples. We will start from the most basic ones and continue up. SQL queries will be organized chronologically according to their difficulty. I will add more later on. SQL knowledge is a must for any IT department nowadays.… Read More »
This mini-article is made for beginners. We will take a closer look on how to write a simple T-SQL script and I will also explain basic sql commands. We will put together individual parts of script piece by piece and we will understand its purpose during the process. Let’s dig into SQL basics in following… Read More »
GROUP BY clause is used to group data. In most of the cases, we talk of a situation when we need to make an aggregate operation in the table (sum of sales, number of records, average, etc.) GROUP BY in SQL Script SELECT FROM WHERE GROUP BY HAVING ORDER BY Syntax SELECT [Column 1], [Column… Read More »
HAVING clause is a special type of SQL command. It works in a similar way as WHERE clause and we use it to define a condition. There are important differences between the two clauses. Let me explain the differences between SQL HAVING and WHERE. Having in SQL script SELECT FROM WHERE GROUP BY HAVING ORDER… Read More »
ORDER BY clause in SQL enables us to sort results of the query by specific field (column) or more columns. There are 2 sorting options: Ascending order (ASC) – sorts records from lowest to highest in case of numbers and from A to Z in case of text strings Descending order (DESC) – sorts records… Read More »
WHERE clause is used to define limit requirements for queries. We are not interested in all records in most cases of queries into tables. Only some subsets of the records based on set criteria are of our interest. Order of WHERE Clause in SQL Script SELECT FROM WHERE GROUP BY HAVING ORDER BY Syntax SELECT… Read More »
When you work with SQL database you usually need more than 1 table. Some values are in one table and the others are in a different one = division of the information into many tables which are connected between each other (via keys) is the principle of relational database. There are 5 basic kinds of… Read More »
When you work with SQL database you usually need more than 1 table. Some values are in one table and the others are in a different one = division of the information into many tables which are connected between each other (via keys) is the principle of relational database. There are 5 basic kinds of… Read More »
When you work with SQL database you usually need more than 1 table. Some values are in one table and the others are in a different one = distribution of data into many tables which are connected between each other (via keys) is the principle of relational database. There are 5 basic kinds of joins:… Read More »
When we work with SQL database we usually need to work with more than 1 table. Some values are in one table and the others are in a different one = distribution of data into many tables which are connected between each other (via keys) is the principle of relational database. There are 5 basic… Read More »
SELECT clause is used to gain data from a table. This clause is followed by a list of columns, which we need to display. SELECT must always be used in combination with clause FROM by which we state from which table we want the data to be selected. Ideally, we also add clause WHERE which… Read More »