[Introduction to It learning]sql and examples

SQL is a database query language that allows you to query data quickly. In fact, in general, you can also use Excel to query database data.

But people usually think that SQL is more flexible and convenient.

Getting Started with SQL Learning Web site:

Http://www.w3schools.com/SQl/sql_orderby.asp

Https://en.wikipedia.org/wiki/SQL

SQL Learning Notes:

1, if you have a concept of a structured database, then it is easy to understand. If you have no concept of structured database, please Baidu structured database, the database structure, tables, fields, queries (filtering), additions and deletions, sorting data table and other operations have a basic understanding.

2. From the Customers table, query the record of the country field that begins with U.

SELECT * from Customers
WHERE country like "u%";

3. Query the Country field from the Customers table for the USA, and the city fields are Seattle or records that begin with P.

SELECT * from Customers
Where country = "USA" and (city = "Seattle" or city like "p%");

4, from the Customers table to query the City field content of the record content is not repeated, just return to the City field. (Distinct command to return the unique distinct value of a field)

SELECT DISTINCT city from Customers;

5, like statements, s%,%s,%sand%, respectively, the beginning of S, S end, including Sand

SELECT * from Customers
WHERE country like '%land% ';

[Introduction to It learning]sql and examples