slide môn học MySQL bài 6 using basic functions in MySQL

 Use GROUP BY and HAVING clause in MySQL queries  Use the Mathematical functions  Use the Date functions  Use the String functions  Use the system information function... Aggregate

Using Basic Functions in MySQL

Session 12

 Joining of tables means combining two or more data or records

of different tables of same database into one comprehensive structure

 The field with the primary key of a table is used for joining

tables by referring it as a reference key for the next table

 Advantages of joining of tables are:

 Greater ease of manipulation

 Increases speed in access

 Reduces data redundancy

 The tables are joined either with the WHERE clause used with SELECT command or by using JOIN keyword

Review - I

Review - II

 An equi-join can also be called as INNER JOIN An INNER JOIN behaves same like ‘,’ which is used for joining tables

 When using INNER JOIN the common field of the joining

tables should have the matching value

 An OUTER JOIN is used to join two tables, a source and

joining table, which have one or more columns in common

 A self-join is a query in which a value of a table column is

joined or compared to itself

 Use GROUP BY and HAVING clause in

MySQL queries

 Use the Mathematical functions

 Use the Date functions

 Use the String functions

 Use the system information function

Basics of Using Functions

 The functions used in MySQL are similar to any

other programming language

 A function is used in two ways in a MySQL

command:

 Value to be retrieved

 Part of a WHERE clause

Using GROUP BY and HAVING Clause

 GROUP BY clause groups the rows with similar values for a specific column into a single row

 HAVING clause is used to define the result set based on some set of calculations

 GROUP BY clause is used with aggregate functions

 The aggregate functions are AVG, COUNT, MAX, MIN,

and SUM

Aggregate Functions - I

 AVG function

 Returns the average of the values of the argument

 The syntax for obtaining the average of the

Aggregate Functions - II

 MIN function

 Returns the minimum value of the expression

 The syntax for obtaining the smallest value is:

MIN(expression)

 SUM function

 Returns the sum of the values in the expression

 The syntax for obtaining the sum is:

SUM(expression)

Mathematical Functions using

MySQL - I

 MySQL provides with mathematical functions that operate

on data and return numerical value

 Returns cosine of an argument

 The syntax for obtaining the cosine of an argument X is:

COS(X)

Mathematical Functions using

MySQL - II

 CRC function

 Calculates a cyclic redundancy check value

 Returns a 32 bit unsigned value

 The syntax for obtaining the cyclic redundancy

value of an argument X is:

CRC32(X)

Mathematical Functions using

MySQL - III

 EXP function

 Returns the value of e raised to the power of X

 The syntax for obtaining the natural logarithm of

an argument is:

EXP(X)

 FLOOR function

 Returns the largest value not greater than X

 The syntax for obtaining the largest value not

greater than the argument specified is:

FLOOR(X)

Mathematical Functions using

MySQL - IV

 LOG function

 Enables a user to enter one or two arguments

 The syntax for specifying one argument in a LOG

Mathematical Functions using

 Returns a -1, 0, or 1 depending on the argument is

positive, zero, or positive

 The syntax for obtaining the sign of an argument is:

SIGN(X)

Mathematical Functions using

MySQL - VI

 SQRT function

 Returns the non-negative square root of the argument

 The syntax for obtaining the square root of an argument is:

SQRT(X)

Date Functions in MySQL - I

 MySQL provides with date functions that operate on date and time data type

 ADDDATE function

 Add two date expressions

 The syntax for adding two date expressions is:

ADDDATE(expr1,days)

Date Functions in MySQL - II

Date Functions in MySQL - III

 Returns the name of the weekday for a date

 The syntax for obtaining the name of the week day is:

DAYNAME(date)

Date Functions in MySQL - IV

 MONTHNAME function

 Returns the name of the month for the date

 The syntax for obtaining the month name is:

MONTHNAME (date)

 YEAR function

 Returns the year for the date

 The syntax for obtaining the year for a date argument is: YEAR (date)

String Functions Using MySQL - I

 String Functions operate on character type of data

String Functions Using MySQL - II

 BIN function

 Returns a string representation of the binary value

of N, where N is the BIGINT number

 The syntax for obtaining the string representation

is:

BIN(string)

 CONCAT function

 Returns a string after concatenating the arguments

 The syntax to concatenate is:

CONCAT(STR1,STR2, )

String Functions Using MySQL - III

 BIT_LENGTH function

 Returns the length of the string specified as the argument

 The syntax for obtaining the length of the string in bits is:

String Functions Using MySQL - IV

 LENGTH function

 Returns the length of a string in bytes

 The syntax for obtaining the length of the string is:

String Functions Using MySQL - V

 Adds a string to a string at a specified position

 The syntax for insert function is:

INSERT(str,pos,len,newstr)

String Functions Using MySQL - VI

 LOWER function

 Changes the string entered into lowercase

 The syntax for converting into lower case is:

LOWER(str)

System Information Functions using MySQL - I

 System information functions returns the system related

information

 BENCHMARK function

 Executes the expression entered as the argument

repeatedly the number of times specified in the argument

 The syntax for benchmark is:

BENCHMARK(count, expr)

System Information Functions using MySQL - II

 CHARSET function

 Returns the character set of the argument

 The syntax for obtaining the character set of a

string is:

CHARSET (str)

 CONNECTION_ID function

 Returns the thread ID for the connection

 The syntax for obtaining the thread ID is:

CONNECTION_ID ()

System Information Functions using MySQL - III

 Returns the name of the current database

 The syntax for obtaining the database name is:

DATABASE()

System Information Functions using MySQL - IV

 VERSION function

 Returns version of MySQL

 The syntax for obtaining the version is:

VERSION()

Summary – I

 The functions are used in two ways in the SQL queries:

 In place of the column name

 In the WHERE clause

 The GROUP BY clause is used with the functions to group the data on a specific constraint

 The mathmematical functions are used to operate on

numbers The examples of mathematical functions are COS, SIN, TAN, and several others

 The mathematical fuction returns a NULL value if error occurs while processing

Summary – II

 The string function operates on character type of data

 The date functions are used to perfom computations on the date type fo data These fucntions are used to add the date, subtract the date, and extract a part of the date.

 The system functions are used to obtain sytem related information