All articles: Data Definition Language (DDL)

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How to call an Oracle check constraints – Querychat
In this article, we will discover what is the Oracle syntax checker, what does it do and how it can be used in our work. Also, we will find out how to enable or disable the check constraints. What is the Oracle syntax checker? If we need to check whether...
How to Work with the Table Function in Oracle – Querychat
In this article, we will check how the Oracle PL SQL table function works, including examples, for better understanding. When working with PL/SQL collections, we may need to work with them as a regular table, and that is what the table function is needed. This function allows the PL/SQL collections...
Find Database Name in SQL – Querychat
In this article, we are going to discuss, how to find database names, how to find the current database and how to set the current database. Detailed information and examples are included for both SQL Server and MySQL. How to find Database Names in MySQL The below command is used...
Setting the NLS_DATE_FORMAT parameter in Oracle – Querychat
Oracle offers various initialization parameters whose value defines the behavior of the database. The value of these variable initialization parameters can be modified to improve the system's performance.  In this article, we will learn about the Oracle nls_date_format parameter, how to check its default value, and different ways of modifying...
The Main SQL Terms Used in the Query Code – Querychat
In this article, we will discover what the main SQL terms are and what is the purpose of their use. Also, we will look at practical examples. What are SQL terms By terms, we mean the statements, which are the foundation of the query code. Statements are what SQL consists...
MySQL Column Count and Row Size limitations – Querychat
In this article, we will check on the Column count and row size limitations for MySQL tables, including several examples for better understanding. Column Count Limitations The maximum amount of columns allowed in a table for MySQL is 4096. Depending on certain aspects, this amount can less than 4096 per...
MySQL InnoDB Row Formats – Querychat
In this article, we will check the MySQL InnoDB Row formats, and how to define it, including simplified examples for better understanding. By knowing how to save information in a specific format, we can improve performance for DML statements. It can help us save storage space, decreasing queries response time,...
How to work with SQLite create table if not exists and drop table if exists sentences – Querychat
In this article, we will learn how to use the SQLite create table if not exist and SQLite drop table if exists statements. SQLite create table if not exists This clause must be placed at the beginning of the sentence we use to create a table. Its function is to...
How to Debug and Fix MySQL Error 1022 – Querychat
In RDBMS, foreign keys are used to represent a relationship between two tables. While creating the child table, a foreign key constraint is created that refers to the primary key of the parent table. In this article, we will learn how to debug and solve MySQL Error 1022, which is...
Understanding the Concept of Weak Entity in RDBMS – Querychat
In this article, we will understand the concept of a weak entity, their representation in ER-Diagram, and the difference between Strong and weak entity. Entity An Entity is an identifiable object in the real world that can have physical or conceptual existence. The examples of an entity with physical existence...
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