SQL follows some unique set of rules and guidelines called syntax. .
- SQL is not case sensitive. Generally SQL keywords are written in uppercase.
- SQL statements are dependent on text lines. We can place a single SQL statement on one or multiple text lines.
- You can perform most of the action in a database with SQL statements.
- SQL depends on relational algebra and tuple relational calculus.
SQL statements are started with any of the SQL commands/keywords like SELECT, INSERT, UPDATE, DELETE, ALTER, DROP etc. and the statement ends with a semicolon (;). Example of SQL statement:
SELECT "column_name" FROM "table_name";
Semicolon is used to separate SQL statements. It is a standard way to separate SQL statements in a database system in which more than one SQL statements are used in the same call. In this tutorial, we will use semicolon at the end of each SQL statement.
These are the some important SQL command:
SELECT: it extracts data from a database.
UPDATE: it updates data in database.
DELETE: it deletes data from database.
CREATE TABLE: it creates a new table.
ALTER TABLE: it is used to modify the table.
DROP TABLE: it deletes a table.
CREATE DATABASE: it creates a new database.
ALTER DATABASE: It is used to modify a database.
INSERT INTO: it inserts new data into a database.
CREATE INDEX: it is used to create an index (search key).
DROP INDEX: it deletes an index.