Reviewing SQL Concepts
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The document provides an introduction to SQL (Structured Query Language), detailing its history, purpose, and functionalities. SQL is a standardized language for accessing and managing data in databases, enabling tasks such as data retrieval, insertion, updating, and deletion. It also outlines basic SQL syntax and examples for common operations like SELECT and WHERE clauses.
Reviewing SQL Concepts
- 1. Reviewing SQL concepts Prof. Hitesh Mohapatra
- 2. Introduction to SQL SQL is a standard language for storing, manipulating and retrieving data in databases. How to pronounce SQL properly? S-Q-L or Sequel?
- 3. According to Wikipedia: SQL was initially developed at IBM by Donald D. Chamberlin and Raymond F. Boyce after learning about the relational model from Ted Codd in the early 1970s. This version, initially called SEQUEL (Structured English Query Language), was designed to manipulate and retrieve data stored in IBM’s original quasi-relational database management system, System R, which a group at IBM San Jose Research Laboratory had developed during the 1970s.
- 4. What is SQL? • SQL stands for Structured Query Language • SQL lets you access and manipulate databases • SQL became a standard of the American National Standards Institute (ANSI) in 1986, and of the International Organization for Standardization (ISO) in 1987.
- 5. What Can SQL do? • SQL can execute queries against a database • SQL can retrieve data from a database • SQL can insert records in a database • SQL can update records in a database • SQL can delete records from a database • SQL can create new databases • SQL can create new tables in a database • SQL can create stored procedures in a database • SQL can create views in a database • SQL can set permissions on tables, procedures, and views
- 6. SQL Syntax A database most often contains one or more tables. Each table is identified by a name (e.g. "Customers" or "Orders"). Tables contain records (rows) with data. *The table above contains five records (one for each customer) and seven columns (CustomerID, CustomerName, ContactName, Address, City, PostalCode, and Country).
- 7. SQL Statements Most of the actions you need to perform on a database are done with SQL statements. The following SQL statement selects all the records in the "Customers" table: SELECT * FROM Customers; SQL keywords are NOT case sensitive: select is the same as SELECT
- 8. Semicolon after SQL Statements? • SELECT - extracts data from a database • UPDATE - updates data in a database • DELETE - deletes data from a database • INSERT INTO - inserts new data into a database • CREATE DATABASE - creates a new database • ALTER DATABASE - modifies a database • CREATE TABLE - creates a new table • ALTER TABLE - modifies a table • DROP TABLE - deletes a table • CREATE INDEX - creates an index (search key) • DROP INDEX - deletes an index
- 9. SQL SELECT Statement The SELECT statement is used to select data from a database. The data returned is stored in a result table, called the result-set. SELECT Syntax SELECT column1, column2, ... FROM table_name; Here, column1, column2, ... are the field names of the table you want to select data from. If you want to select all the fields available in the table, use the following syntax: SELECT * FROM table_name;
- 10. SELECT Column Example The following SQL statement selects the "CustomerName" and "City" columns from the "Customers" table: SELECT CustomerName, City FROM Customers; SELECT * Example The following SQL statement selects all the columns from the "Customers" table: SELECT * FROM Customers;
- 11. SQL WHERE Clause The WHERE clause is used to filter records. The WHERE clause is used to extract only those records that fulfill a specified condition. WHERE Syntax SELECT column1, column2, ... FROM table_name WHERE condition; Example: SELECT * FROM Customers WHERE Country='Mexico';