How to select data in the SQL

Selecting Data

The select statement is used to query the database and retrieve selected data that match the criteria that you specify. Here is the format of a simple select statement:

select "column11"
  [,"column12",etc] 
  from "tablename"
  [where "condition"];
  [] = optional

The column names that follow the select keyword determine which columns will be returned in the results. You can select as many column names that you'd like, or you can use a "*" to select all columns.

The table name that follows the keyword from specifies the table that will be queried to retrieve the desired results.

The where clause (optional) specifies which data values or rows will be returned or displayed, based on the criteria described after the keyword where.

Conditional selections used in the where clause:

=	Equal
>	Greater than
<	Less than
>=	Greater than or equal
<=	Less than or equal
<>	Not equal to
LIKE	*See note below

The LIKE pattern matching operator can also be used in the conditional selection of the where clause. Like is a very powerful operator that allows you to select only rows that are "like" what you specify. The percent sign "%" can be used as a wild card to match any possible character that might appear before or after the characters specified.

 For example:

select first, last, city
   from empinfo
   where first LIKE 'Pu%';

This SQL statement will match any first names that start with 'Pu'. Strings must be in single quotes.

Or you can specify,

select first, last
   from empinfo
   where last LIKE '%d';

This statement will match any last names that end in a 'd'.

select * from empinfo
   where first = 'Pune';

This will only select rows where the first name equals 'Pune' exactly.

Sample Table: empinfo
first	last	id	age	city	state
John	sons	90901	45	Delhi	Delhi
Mary	coms	90902	25	Punjab	Punjab
Eric	wards	80801	32	Pune	Maharastra
Mary Com	Edwards	80802	32	hyderabad	Telangana
Ginger	well	90802	42	Chennai	Tamilanadu
Sebastian	Wala	98001	23	Goa	Goa
Gussa	Gray	20802	35	Banglore	Karnataka
Mary Com	May	30802	52	Mumbai	Maharastra
Erisca	Williams	32427	60	Noida	Haryana
Lebroy	Lable	34243	22	Luknow	UP
Emma	Clever	33343	22	Kolkata	Bengal

Try the below sample select statements at home.

select first, last, city from empinfo; 

select last, city, age from empinfo
       where age > 30; 

select first, last, city, state from empinfo
       where first LIKE 'S%'; 

select * from empinfo; 

select first, last, from empinfo
       where last LIKE '%s'; 

select first, last, age from empinfo
       where last LIKE '%ary%'; 

select * from empinfo where first = 'Erisc';

What is SQL & Basics of Tables?

What is SQL?

SQL stands for Structured Query Language. SQL is used to communicate with a database. According to ANSI (American National Standards Institute), it is the standard language for relational database management systems. SQL statements are used to perform tasks such as update data on a database, or retrieve data from a database. Some common relational database management systems that use SQL are: Oracle, Sybase, Microsoft SQL Server, Access, Ingres, etc. Although most database systems use SQL, most of them also have their own additional proprietary extensions that are usually only used on their system. However, the standard SQL commands such as "Select", "Insert", "Update", "Delete", "Create", and "Drop" can be used to accomplish almost everything that one needs to do with a database. This tutorial will provide you with the instruction on the basics of each of these commands as well as allow you to put them to practice using the SQL Interpreter.

Table Basics

A relational database system contains one or more objects called tables. The data or information for the database are stored in these tables. Tables are uniquely identified by their names and are comprised of columns and rows. Columns contain the column name, data type, and any other attributes for the column. Rows contain the records or data for the columns. Here is a sample table called "weather Report".

city, state, high, and low are the columns. The rows contain the data for this table:

Weather Report
city	state	high	low
Hyderabad	Telangana	100	85
Mumbai	MH	102	92
New Delhi	Delhi	86	69
Bangaluru	Karnataka	79	60
Ahmadabad	Gujarat	85	72