What is SQL?
SQL stands for Stuctured Query Language. It is a domain-specific language used in programming and designed for managing data held in a relational database management system (RDBMS), or for stream processing in a relational data stream management system (RDSMS).
However, in this article I will introduce what is SQL, what are some elements in SQL, how to name things, and what are some data types in SQL.
In this new category I will introduce some of the common statements in SQL and I will divide them into sections, which include:
- What is SQL?
- What is the Language Elements
- Naming things
- Data types
- Using SELECT
- WHERE Clause
- AND and OR
- IS and IS NOT
- JOINS (LEFT JOIN, RIGHT JOIN, FULL JOIN)
- ORDER BY
- GROUP BY
- (Adding, removing, and deleting data) INSERT, UPDATE, DELETE
- Creating tables (ALTER, DROP, CREATE TABLE)
- null OR NOT NULL
- PRIMARY KEY, AND CONSTRAINTS
The SQL language is subdivided into several language elements, including:
- Clauses, which are constituent components of statements and queries. (In some cases, these are optional.)
- Expressions, which can produce either scalar values, or tables consisting of columns and rows of data
- Predicates, which specify conditions that can be evaluated to SQL three-valued logic (3VL) (true/false/unknown) or Boolean truth values and are used to limit the effects of statements and queries, or to change program flow.
- Queries, which retrieve the data based on specific criteria. This is an important element of SQL.
- Statements, which may have a persistent effect on schemata and data, or may control transactions, program flow, connections, sessions, or diagnostics.
- SQL statements also include the semicolon (“;”) statement terminator. Though not required on every platform, it is defined as a standard part of the SQL grammar.
- Insignificant whitespace is generally ignored in SQL statements and queries, making it easier to format SQL code for readability.
Stay tuned for the next article when I go deeper into the syntax of SQL language. Here’s what I will feature next:
- Using SELECT
- the FROM clause
Thanks for reading!