A glossary of key terms related to SQL

11. INSERT

An SQL statement used to add new rows of data to a table.

12. UPDATE
    An SQL statement used to modify existing data in a table.
13. DELETE

An SQL statement used to remove rows from a table.

14. JOIN
    An SQL operation that combines rows from two or more tables based on a related column between them. Types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN.
15. WHERE
    A clause used in SQL queries to filter records based on specific conditions. It is used with SELECT, UPDATE, and DELETE statements.
16. GROUP BY
    A clause used in SQL to group rows that have the same values in specified columns, often used with aggregate functions like COUNT, SUM, AVG, etc.
17. HAVING
    A clause used to filter groups of rows created by the GROUP BY clause, typically based on an aggregate function.
18. ORDER BY
    A clause used to sort the result set of a query by one or more columns, either in ascending (ASC) or descending (DESC) order.
19. DISTINCT
    A keyword used in SQL to return only distinct (unique) values from a column or combination of columns.
20. Aggregate Functions

Functions in SQL that perform a calculation on a set of values and return a single value. Common aggregate functions include COUNT, SUM, AVG, MIN, and MAX.

21. Subquery
    A query nested within another SQL query. Subqueries are often used in SELECT, INSERT, UPDATE, or DELETE statements to operate on data returned by the subquery.
22. View
    A virtual table in SQL that is the result of a stored query. Views allow users to simplify complex queries and provide a level of abstraction.
23. Stored Procedure
    A set of SQL statements stored in the database and executed as a single unit. Stored procedures can include control-of-flow language, which allows for the implementation of logic like loops and conditionals.
24. Trigger
    A database object that automatically executes a specified SQL statement when a particular event occurs, such as an INSERT, UPDATE, or DELETE operation on a table.
25. Constraint

A rule enforced on data columns in a table to ensure the integrity and accuracy of the data. Common constraints include PRIMARY KEY, FOREIGN KEY, UNIQUE, NOT NULL, and CHECK.

26. Normalization

The process of organizing data in a database to reduce redundancy and improve data integrity by dividing large tables into smaller, related tables.

27. Denormalization
    The process of combining tables to increase data retrieval speed at the cost of introducing redundancy.
28. Transaction
    A sequence of one or more SQL operations executed as a single unit. Transactions are typically governed by the ACID properties (Atomicity, Consistency, Isolation, Durability).
29. ACID Properties

A set of properties that guarantee the reliability of database transactions:

• Atomicity: Ensures that all operations within a transaction are completed; otherwise, the transaction is aborted.
• Consistency: Ensures that a transaction brings the database from one valid state to another.
• Isolation: Ensures that concurrent transactions do not interfere with each other.

• Durability:Ensures that the results of a transaction are permanently stored in the database once committed.

30. Schema
    The structure or blueprint of a database, defining how data is organized in tables, relationships, and other database objects.
31. Cursor
    A database object used to retrieve, manipulate, and navigate through a result set row-by-row, often used in stored procedures.
32. Alias
    A temporary name given to a table or column for the duration of a query, making it easier to reference in complex queries.
33. Wildcards
    Special symbols used in SQL queries to search for data within a pattern. Common wildcards include % (matches zero or more characters) and _ (matches a single character).
34. UNION
    An SQL operator used to combine the result sets of two or more SELECT queries, removing duplicate rows in the combined result set.
35. NULL
    A special marker in SQL that indicates the absence of a value in a column. NULL is not equivalent to an empty string or zero.
36. CASE
    A conditional expression in SQL that allows for if-then-else logic within SQL statements, particularly within SELECT statements.
37. Index Scan
    A database operation that sequentially reads all the entries in an index to find the matching rows, used to speed up query performance.
38. Cross Join
    An SQL operation that returns the Cartesian product of two tables, meaning it pairs each row of the first table with each row of the second table.
39. Scalar Function
    A function in SQL that takes one or more input values and returns a single output value. Examples include UPPER(), LOWER(), and ROUND().
40. SET
    An SQL statement used to assign values to variables or to modify data in a table without the use of INSERT, UPDATE, or DELETE commands.