This chapter is from the book
This chapter is from the book
This chapter is from the book
Introduction to SQL
The Structured Query Language, known as SQL, is the language used to talk to most databases. All the previously mentioned databases understand this language, which allows you to talk to them. SQL is a very powerful language and can be a little complicated the further you dive into it. But for now, you only need to know a few frequently used commands.
TABLE 1–2 SQL Basics
|
Keyword |
Definition and Usage |
|
SELECT |
Used to select data from the database Usage SELECT * FROM table Note: The (*) selects all fields in the specified table. |
|
INSERT |
Used to insert new information into the database Usage INSERT INTO table (field1,field2) Values ('Micah','Mike')
|
|
DELETE |
Used to delete data from a database Usage DELETE FROM table WHERE name = 'Mike' |
|
UPDATE |
Used to update data in the database Usage UPDATE table SET Name1 = 'Mike', Name2 = 'Micah' |
TABLE 1–3 SQL Basics—Attributes
|
Keyword |
Definition and Usage |
|
WHERE |
Used to select a certain record Usage SELECT * FROM table WHERE name = 'Micah' |
|
ASC |
Used to sort results in ascending order Usage SELECT * FROM table |
|
DESC |
Used to sort results in descending order Usage SELECT * FROM table WHERE name = 'Mike' DESC |
|
ORDER BY |
Used to sort results by a field name Usage SELECT * FROM table ORDER BY name |
|
DISTINCT |
Used to list distinct field names. If multiple names appear in a field column, only one is returned. Usage SELECT DISTINCT category FROM table |
|
LIKE |
Used to search a field for certain text Usage SELECT * FROM table WHERE name LIKE '%Mike%' Note: The "%" is a wildcard character that returns all records containing the string 'Mike'. |
|
AND |
Condition used to ensure two or more fields of information hold true Usage SELECT * FROM table WHERE fName = 'Mike' AND lName = 'Fredrick' |
|
OR |
Condition used to ensure that any of the two or more fields of information holds true Usage SELECT * FROM table WHERE fName = 'Mike' OR fName = 'Micah' |
|
BETWEEN |
Condition used to return a result within a certain range Usage SELECT * FROM table WHERE birthDate BETWEEN '01' AND '10' |
|
IN |
Condition used to return any specified results in a field Usage SELECT *
FROM table
WHERE birthDate IN ('01','10','23')
|
|
= |
Equal to operator, used to find exact matches; mostly used with WHERE clause |
|
<> |
Not equal to operator, used to return results that do not equal; used with the WHERE clause |
|
> |
Greater than operator |
|
>= |
Greater than or equal to operator |
|
< |
Less than operator |
|
<= |
Less than or equal to operator |