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Valeri Tandilashvili's MySQL Notes
Results: 175
TRUNCATE
Deletes all the rows from 
notes
table
TRUNCATE notes;
The same as the query above - deletes all rows
TRUNCATE TABLE notes;
Note: The two queries are aliases for each other
DROP TABLE
Deletes the table 
notes
with its content
DROP TABLE notes;
If the table does not exist, it will generate the following error:
#1051 - Unknown table 'notes
Deletes several tables at the same time
DROP TABLE notes, students;
Deletes the table if exists, otherwise it will not generate an error
DROP TABLE IF EXISTS notes;
Note: There is no undo. Once we delete, the table is gone
CONV
Converts the first argument from one number system (the second argument) to another (the third argument) Converts 
5
from 
10
base system to 
2
SELECT
    CONV(5, 10, 2)
POWER
Raises the first argument to the power of another argument. The code below returns 
16
because 
2
to the power of 
4
is 
16
SELECT 
    POWER(2, 4)
Note: 
POW
and 
POWER
are the aliases for the same command
RADIANS / DEGREES
These two functions are opposite to each other. 
180
degrees converted to radians gives us 
PI
: 
3.141592653589793
PI
: 
3.141592653589793
radians converted to degrees gives us 
180
degrees.
SELECT
    RADIANS(180),
    DEGREES(3.141592653589793)
RADIANS
Converts degrees to radians. 
90
degrees converted to radians gives us half of 
PI
: 
1.5707963267948966
. 
180
degrees converted to radians gives us 
PI
: 
3.141592653589793
.
SELECT
    RADIANS(90),
    RADIANS(180)
CEIL
Rounds the number up to the lowest integer value greater than the passed decimal argument. Both of the arguments will be rounded to 
3
SELECT
    CEIL(2.3),
    CEIL(2.8)
FLOOR
Rounds the argument down to the greater integer less then the decimal argument. Both of the arguments will be rounded down to 
2
SELECT
    FLOOR(2.3),
    FLOOR(2.8)
ROUND
Rounds the passed value using standard Math rules. The first argument 
2.3
will be rounded to 2 and the second 
2.5
becomes 3
SELECT
    ROUND(2.3),
    ROUND(2.5)
RPAD
The function 
RPAD
appends string (third parameter) the specified number of times (second parameter) to the first parameter. In this example each one of the student's last name that is less than 10 characters long, is filled with 
-
SELECT 
    RPAD(first_name, 10, '-') AS 'student name'
FROM students
Results: 175