Chuanzhi Podcast Liu Daocheng MySql series video material sharing

MySQL is a relational database management system developed by the Swedish MySQL AB company and is currently a product of Oracle. MySQL is one of the most popular relational database management systems. In terms of WEB applications, MySQL is the best RDBMS (Relational Database Management System) application software.

MySQL is a fast, easy-to-use RDBMS used by many small and large businesses. "Chuangzhi Podcast Liu Daocheng MySql Video Tutorial Series" will tell you why the open source MySQL has become so popular, from shallow to deep, and through various practical operations and cases, you will experience the advantages of the MySQL database.

Video playback address: http://www.php.cn/course/245.html

Difficulties in learning databases It is query operations and some functions:

Mathematical function

ABS(x) Returns the absolute value of x

BIN(x) Returns the binary value of x (OCT returns octal, HEX returns hexadecimal)

CEILING(x) Returns the smallest integer value greater than x

EXP(x) Returns the value e (the base of the natural logarithm) x power

FLOOR(x) Returns the largest integer value less than x

GREATEST(x1,x2,...,xn) returns the largest value in the set

LEAST(x1,x2,...,xn) Returns the smallest value in the set

LN(x) Returns the natural logarithm of x

LOG(x,y) Returns the natural logarithm of x Logarithm of base y

MOD(x,y) Returns the modulus (remainder) of x/y

PI() returns the value of pi (pi)

RAND () returns a random value between 0 and 1. You can make the RAND() random number generator generate a specified value by providing a parameter (seed).

ROUND(x,y) Returns the rounded value of parameter x with y decimal places

SIGN(x) Returns the value of the sign representing the number x

SQRT( x) Returns the square root of a number

TRUNCATE(x,y) Returns the result of number x truncated to y decimal places

2. Aggregation function (commonly used in GROUP In the SELECT query of the BY clause)

AVG(col) returns the average value of the specified column

COUNT(col) returns the number of non-NULL values ​​in the specified column

MIN (col) Returns the minimum value of the specified column

MAX (col) Returns the maximum value of the specified column

SUM(col) Returns the sum of all values ​​of the specified column

GROUP_CONCAT (col) Returns the result formed by concatenating column values ​​belonging to a group

3. String function

ASCII(char) returns the ASCII code value of the character

BIT_LENGTH(str) returns the bit length of the string

CONCAT(s1,s2...,sn) concatenates s1,s2...,sn into a string

CONCAT_WS(sep,s1,s2...,sn) concatenates s1,s2...,sn into strings and separate them with sep characters

INSERT(str,x,y,instr) The string str starts from the Position in the list

LCASE(str) or LOWER(str) Returns the result of changing all characters in the string str to lowercase

LEFT(str,x) Returns the result in the string str The leftmost x characters

LENGTH(s) returns the number of characters in the string str

LTRIM(str) Cuts the leading spaces from the string str

POSITION(substr,str) Returns the position of the first occurrence of substring substr in string str

QUOTE(str) Use backslash to escape the single quotation mark in str

REPEAT( str, srchstr, rplcstr) Returns the result of string str repeated x characters on the right

RTRIM(str) Returns the spaces at the end of the string str

STRCMP(s1,s2) Compares the strings s1 and s2

TRIM(str) Remove all spaces at the beginning and end of the string

UCASE(str) or UPPER(str) Return the result of converting all characters in the string str to uppercase

4. Date and time functions

CURDATE() or CURRENT_DATE() returns the current date

CURTIME() or CURRENT_TIME() returns the current time

DATE_ADD(date, INTERVAL int keyword) returns the result of date plus interval time int (int must be formatted according to the keyword), such as: SELECTDATE_ADD(CURRENT_DATE,INTERVAL 6 MONTH);

DATE_FORMAT(date,fmt) as specified The fmt format formats the date value

DATE_SUB(date,INTERVAL int keyword) returns the result of date plus interval time int (int must be formatted according to the keyword), such as: SELECTDATE_SUB(CURRENT_DATE,INTERVAL 6 MONTH);

DAYOFWEEK(date) Returns the day of the week represented by date (1~7)

DAYOFMONTH(date) Returns the day of the month represented by date (1~31)

DAYOFYEAR(date) Returns the day of the year that date is (1~366)

DAYNAME(date) Returns the day of the week name of date, such as: SELECT DAYNAME( CURRENT_DATE);

FROM_UNIXTIME(ts,fmt) Format UNIX timestamp ts according to the specified fmt format

HOUR(time) Return the hour value of time (0~23)

MINUTE(time) Returns the minute value of time (0~59)

MONTH(date) Returns the month value of date (1~12)

MONTHNAME(date) Returns the month name of date, such as: SELECT MONTHNAME(CURRENT_DATE);

NOW() Return the current date and time

QUARTER(date) Return date in the quarter of the year (1~4), such as SELECT QUARTER(CURRENT_DATE);

WEEK(date) Return date It is the week of the year (0~53)

YEAR(date) Returns the year of date (1000~9999)

The lecturer of this course is Liu Daocheng, a famous lecturer of Chuanzhi Podcast. Maybe you don’t know Liu Daocheng, but when it comes to Yan Shiba, you must know that Liu Daocheng is Yan Shiba. His lecture style is humorous and the classroom atmosphere is very good, which can mobilize students' enthusiasm in class and give everyone a relaxed learning atmosphere. In addition, his lectures are very focused, allowing you to know where the key points of learning are, and you can focus on studying when you go back. The difficult points of learning will also be explained in great detail, so that everyone can understand them.

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