All articles: Data Query Language (DQL)

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DOUBLE, DECIMAL, FLOAT & Negative Numbers in MySQL – Querychat
In this article, we discuss how to choose suitable mixed decimal data types and options to store negative numbers in MySQL. We specifically emphasize on decimals, double and floats and differences between them. Double Double is a data type that is used to store floating-point numbers. Therefore double can represent negative...
SQL Server Identity Property – Querychat
The SQL Server IDENTITY property allows us to create a column whose value will uniquely identify a row within a table.  The created column is referred to as an identity column: it behaves like a counter that automatically creates a unique value for a specified table column.  An identity column...
SQL Server SOUNDEX and DIFFERENCE Functions – Querychat
The two functions, DIFFERENCE and SOUNDEX, both work with character strings in order to evaluate those that sound similar, based on English phonetic rules. In this article, we will discuss these functions, their use, and take a look at some examples of using them. T-SQL SOUNDEX and DIFFERENCE Finding similarities...
MySQL Format Function – Querychat
While manipulating data in MySQL, we often need to present a particular numerical value in some format that is different from the default one. This article elaborates on how to use the FORMAT function to change the default format of a numerical value. The Syntax of MySQL FORMAT Function The...
Views in SQL Server – Querychat
While developing databases and providing user access to data, sometimes it is very important to have the possibility to create virtual tables for both security and efficiency reasons. Those virtual tables are called views. This article elaborates on the advantages of views in SQL Server, as well as how to...
SP_REFRESHVIEW in SQL Server – Querychat
SP_REFRESHVIEW is a system procedure that enables us to update the view’s definition in SQL Server. In this article, we will learn about refreshing views in terms of using the SP_REFRESHVIEW stored procedure. What is SP_REFRESHVIEW? SP_REFRESHVIEW is a system procedure that we use when we want to refresh the...
Boolean Data in SQL – Querychat
In this article, we are going to learn how to insert and update boolean data in SQL. How we retrieve data using a boolean condition. Included examples can be executed in both SQL Server and MySQL. Boolean Data Some properties have only two options true or false, and yes or...
Understanding Oracle all_tab_columns – Querychat
Oracle stores all the information about tables, views, columns, triggers, and other database objects in Oracle’s build-in-views, also known as data dictionary tables. In this article, we will learn about Oracle’s ‘all_tab_columns’ data dictionary view and its structure. all_tab_columns Whenever a table or view is created or modified in a...
How to work with regular expressions in SQL Server – Querychat
In this article, we will learn how to work with regular expressions in SQL Server. We will build some example queries with different search patterns so we can get familiar with the search pattern design process. We are going to build our sample queries based on a table that we...
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