SQL Syntax

  • The syntax of a language describes the language elements.
  • SQL statements are somewhat like simple English sentences.
  • Keywords include SELECT, UPDATE, WHERE, ORDER BY, etc.
  • ANSI Standard SQL is the lingua franca for relational databases.
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The SQL Syntax


SQL was designed to be entered on a console and results would display back to a screen.

Today, SQL is mostly used by programmers who use SQL inside their language to build applications that access data in a database.


Four fundamental operations that apply to any database are:


  1. Read the data  --  SELECT
  2. Insert new data  --  INSERT
  3. Update existing data  --  UPDATE
  4. Remove data  --  DELETE

Collectively these are referred to as CRUD (Create, Read, Update, Delete).

The general form for each of these 4 operations in SQL is presented next.




The SQL SELECT general form

SELECT column-names
FROM table-name
WHERE condition
ORDER BY sort-order

Example:
SELECT FirstName, LastName, City, Country 
FROM Customer
WHERE City = 'Paris'
ORDER BY LastName




The SQL INSERT general form

INSERT table-name (column-names)
VALUES (column-values)

Example:
INSERT Supplier (Name, ContactName, City, Country)
VALUES ('Oxford Trading', 'Ian Smith', 'Oxford', 'UK')




The SQL UPDATE general form

UPDATE table-name
SET column-name = column-value
WHERE condition

Example:
UPDATE OrderItem
SET Quantity = 2
WHERE Id = 388




The SQL DELETE general form

DELETE table-name
WHERE condition

Example:
DELETE Customer
WHERE Email = 'alex@gmail.com'