The process of connecting to and retrieving data that is stored on large tables with many rows and columns.
Data integrity refers to the accuracy and consistency of data stored in a database or other data storage system. It ensures that the data in the system is reliable, accurate, and consistent over time. How is data integrity maintained? Data integrity is maintained by enforcing data validation rules, referential integrity constraints, and other data integrity…
Normalization is a process of organizing data in a database to reduce data redundancy and ensure data integrity. There are several types of normalization, each with its own set of rules for eliminating data redundancy and improving data integrity. The most commonly used normalization levels are: There are also higher levels of normalization, such as…
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DROP and TRUNCATE are two SQL commands that can be used to remove data from a table, but they work in different ways: How to drop a table from a database It is important to remember that if you have the same name spread over a few databases, you should reference the correct databases, to…
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Denormalization is the process of adding redundant data to a database to improve query performance. It involves intentionally violating the normal forms of database design in order to simplify or speed up queries by reducing the number of joins or eliminating the need for certain indexes. The normal forms of database design are a set…
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Query optimization in SQL refers to the process of improving the performance of SQL queries by selecting the most efficient execution plan for the query. When a SQL query is executed, the database management system (DBMS) must determine the best way to retrieve the requested data from the database. Query optimization involves analyzing the query…
In SQL, a clustered index is a type of index that determines the physical order of the data in a table. It organizes the table data based on the values in one or more columns, and stores the data in the table accordingly. When a clustered index is created on a table, the rows of…
In SQL, a unique key is a constraint that ensures that the values in a column or set of columns are unique across all rows in a table and that the values cannot be null. A unique key is similar to a primary key, but it differs in that it does not necessarily need to…
In SQL, constraints are rules that are enforced on a table’s data to maintain the integrity and accuracy of the data. Constraints can be applied to one or more columns in a table, and they can be added or removed as needed. Here are some of the most common types of constraints in SQL: Constraints…
In SQL, both CHAR and VARCHAR2 are character data types, but they have some differences in terms of their storage and usage. CHAR: VARCHAR2: Here’s an example to illustrate the difference: In the char_test table, the name and address columns are both defined as CHAR, with fixed lengths of 10 and 20 characters, respectively. If…
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SQL(Structured Query Language) and MySQL are related but distinct concepts. SQL is a programming language that is used to manage relational databases, while MySQL is a specific relational database management system (RDBMS) that uses SQL as its query language. Here are some key differences between SQL and MySQL: In summary, SQL is a language used…
