Các chức năng của MySQL
MySQL có nhiều hàm tích hợp sẵn.
Tham chiếu này chứa chuỗi, số, ngày tháng và một số hàm nâng cao trong MySQL.
Hàm chuỗi MySQL
| Function | Description |
|---|---|
| ASCII | Returns the ASCII value for the specific character |
| CHAR_LENGTH | Returns the length of a string (in characters) |
| CHARACTER_LENGTH | Returns the length of a string (in characters) |
| CONCAT | Adds two or more expressions together |
| CONCAT_WS | Adds two or more expressions together with a separator |
| FIELD | Returns the index position of a value in a list of values |
| FIND_IN_SET | Returns the position of a string within a list of strings |
| FORMAT | Formats a number to a format like "#,###,###.##", rounded to a specified number of decimal places |
| INSERT | Inserts a string within a string at the specified position and for a certain number of characters |
| INSTR | Returns the position of the first occurrence of a string in another string |
| LCASE | Converts a string to lower-case |
| LEFT | Extracts a number of characters from a string (starting from left) |
| LENGTH | Returns the length of a string (in bytes) |
| LOCATE | Returns the position of the first occurrence of a substring in a string |
| LOWER | Converts a string to lower-case |
| LPAD | Left-pads a string with another string, to a certain length |
| LTRIM | Removes leading spaces from a string |
| MID | Extracts a substring from a string (starting at any position) |
| POSITION | Returns the position of the first occurrence of a substring in a string |
| REPEAT | Repeats a string as many times as specified |
| REPLACE | Replaces all occurrences of a substring within a string, with a new substring |
| REVERSE | Reverses a string and returns the result |
| RIGHT | Extracts a number of characters from a string (starting from right) |
| RPAD | Right-pads a string with another string, to a certain length |
| RTRIM | Removes trailing spaces from a string |
| SPACE | Returns a string of the specified number of space characters |
| STRCMP | Compares two strings |
| SUBSTR | Extracts a substring from a string (starting at any position) |
| SUBSTRING | Extracts a substring from a string (starting at any position) |
| SUBSTRING_INDEX | Returns a substring of a string before a specified number of delimiter occurs |
| TRIM | Removes leading and trailing spaces from a string |
| UCASE | Converts a string to upper-case |
| UPPER | Converts a string to upper-case |
Các hàm số trong MySQL
| Function | Description |
|---|---|
| ABS | Returns the absolute value of a number |
| ACOS | Returns the arc cosine of a number |
| ASIN | Returns the arc sine of a number |
| ATAN | Returns the arc tangent of one or two numbers |
| ATAN2 | Returns the arc tangent of two numbers |
| AVG | Returns the average value of an expression |
| CEIL | Returns the smallest integer value that is >= to a number |
| CEILING | Returns the smallest integer value that is >= to a number |
| COS | Returns the cosine of a number |
| COT | Returns the cotangent of a number |
| COUNT | Returns the number of records returned by a select query |
| DEGREES | Converts a value in radians to degrees |
| DIV | Used for integer division |
| EXP | Returns e raised to the power of a specified number |
| FLOOR | Returns the largest integer value that is <= to a number |
| GREATEST | Returns the greatest value of the list of arguments |
| LEAST | Returns the smallest value of the list of arguments |
| LN | Returns the natural logarithm of a number |
| LOG | Returns the natural logarithm of a number, or the logarithm of a number to a specified base |
| LOG10 | Returns the natural logarithm of a number to base 10 |
| LOG2 | Returns the natural logarithm of a number to base 2 |
| MAX | Returns the maximum value in a set of values |
| MIN | Returns the minimum value in a set of values |
| MOD | Returns the remainder of a number divided by another number |
| PI | Returns the value of PI |
| POW | Returns the value of a number raised to the power of another number |
| POWER | Returns the value of a number raised to the power of another number |
| RADIANS | Converts a degree value into radians |
| RAND | Returns a random number |
| ROUND | Rounds a number to a specified number of decimal places |
| SIGN | Returns the sign of a number |
| SIN | Returns the sine of a number |
| SQRT | Returns the square root of a number |
| SUM | Calculates the sum of a set of values |
| TAN | Returns the tangent of a number |
| TRUNCATE | Truncates a number to the specified number of decimal places |
Các hàm ngày trong MySQL
| Function | Description |
|---|---|
| ADDDATE | Adds a time/date interval to a date and then returns the date |
| ADDTIME | Adds a time interval to a time/datetime and then returns the time/datetime |
| CURDATE | Returns the current date |
| CURRENT_DATE | Returns the current date |
| CURRENT_TIME | Returns the current time |
| CURRENT_TIMESTAMP | Returns the current date and time |
| CURTIME | Returns the current time |
| DATE | Extracts the date part from a datetime expression |
| DATEDIFF | Returns the number of days between two date values |
| DATE_ADD | Adds a time/date interval to a date and then returns the date |
| DATE_FORMAT | Formats a date |
| DATE_SUB | Subtracts a time/date interval from a date and then returns the date |
| DAY | Returns the day of the month for a given date |
| DAYNAME | Returns the weekday name for a given date |
| DAYOFMONTH | Returns the day of the month for a given date |
| DAYOFWEEK | Returns the weekday index for a given date |
| DAYOFYEAR | Returns the day of the year for a given date |
| EXTRACT | Extracts a part from a given date |
| FROM_DAYS | Returns a date from a numeric datevalue |
| HOUR | Returns the hour part for a given date |
| LAST_DAY | Extracts the last day of the month for a given date |
| LOCALTIME | Returns the current date and time |
| LOCALTIMESTAMP | Returns the current date and time |
| MAKEDATE | Creates and returns a date based on a year and a number of days value |
| MAKETIME | Creates and returns a time based on an hour, minute, and second value |
| MICROSECOND | Returns the microsecond part of a time/datetime |
| MINUTE | Returns the minute part of a time/datetime |
| MONTH | Returns the month part for a given date |
| MONTHNAME | Returns the name of the month for a given date |
| NOW | Returns the current date and time |
| PERIOD_ADD | Adds a specified number of months to a period |
| PERIOD_DIFF | Returns the difference between two periods |
| QUARTER | Returns the quarter of the year for a given date value |
| SECOND | Returns the seconds part of a time/datetime |
| SEC_TO_TIME | Returns a time value based on the specified seconds |
| STR_TO_DATE | Returns a date based on a string and a format |
| SUBDATE | Subtracts a time/date interval from a date and then returns the date |
| SUBTIME | Subtracts a time interval from a datetime and then returns the time/datetime |
| SYSDATE | Returns the current date and time |
| TIME | Extracts the time part from a given time/datetime |
| TIME_FORMAT | Formats a time by a specified format |
| TIME_TO_SEC | Converts a time value into seconds |
| TIMEDIFF | Returns the difference between two time/datetime expressions |
| TIMESTAMP | Returns a datetime value based on a date or datetime value |
| TO_DAYS | Returns the number of days between a date and date "0000-00-00" |
| WEEK | Returns the week number for a given date |
| WEEKDAY | Returns the weekday number for a given date |
| WEEKOFYEAR | Returns the week number for a given date |
| YEAR | Returns the year part for a given date |
| YEARWEEK | Returns the year and week number for a given date |
Các chức năng nâng cao của MySQL
| Function | Description |
|---|---|
| BIN | Returns a binary representation of a number |
| BINARY | Converts a value to a binary string |
| CASE | Goes through conditions and return a value when the first condition is met |
| CAST | Converts a value (of any type) into a specified datatype |
| COALESCE | Returns the first non-null value in a list |
| CONNECTION_ID | Returns the unique connection ID for the current connection |
| CONV | Converts a number from one numeric base system to another |
| CONVERT | Converts a value into the specified datatype or character set |
| CURRENT_USER | Returns the user name and host name for the MySQL account that the server used to authenticate the current client |
| DATABASE | Returns the name of the current database |
| IF | Returns a value if a condition is TRUE, or another value if a condition is FALSE |
| IFNULL | Return a specified value if the expression is NULL, otherwise return the expression |
| ISNULL | Returns 1 or 0 depending on whether an expression is NULL |
| LAST_INSERT_ID | Returns the AUTO_INCREMENT id of the last row that has been inserted or updated in a table |
| NULLIF | Compares two expressions and returns NULL if they are equal. Otherwise, the first expression is returned |
| SESSION_USER | Returns the current MySQL user name and host name |
| SYSTEM_USER | Returns the current MySQL user name and host name |
| USER | Returns the current MySQL user name and host name |
| VERSION | Returns the current version of the MySQL database |