原文地址：https://www.mysqltutorial.org/mysql-string-functions/
This page shows you the most commonly used MySQL string functions that allow you to manipulate character string data effectively.
| Name | Description |
|---|---|
| CONCAT | Concatenate two or more strings into a single string. |
| CONCAT_WS | Return a single string by concatenating multiple strings separated by a specified separator. |
| INSTR | Return the position of the first occurrence of a substring in a string. |
| LENGTH | Get the length of a string in bytes. |
| CHAR_LENGTH | Return the length of a string measured in characters. |
| LEFT | Get a specified number of leftmost characters from a string. |
| LOWER | Return a string converted to lowercase. |
| LOCATE | Return the position of a substring within a given string starting at a specified position. |
| LTRIM | Remove all leading spaces from a string. |
| REPLACE | Replace all occurrences of a substring in a string with a new one. |
| REPEAT | Repeat a string a specified number of time. |
| REVERSE | Reverse a string. |
| RIGHT | Get a specified number of rightmost characters from a string. |
| RTRIM | Remove all trailing spaces from a string. |
| SUBSTRING | Extract a substring starting from a position with a specific length. |
| SUBSTRING_INDEX | Return a substring from a string before a specified number of occurrences of a delimiter. |
| TRIM | Remove unwanted characters from a string. |
| FIND_IN_SET | Find a string within a comma-separated list of strings. |
| FORMAT | Format a number with a specific locale, rounded to the number of decimals. |
| UPPER | Convert a string to uppercase. |
- CONCAT(): Combines two or more strings into a single string.
- CONCAT_WS(): Combines multiple strings into a single string with a specified separator.
- SUBSTRING(): Extracts a substring from a given string.
- SUBSTRING_INDEX(): Extracts a substring from a string using a delimiter.
- LEFT(): Returns a specified number of characters from the beginning of a string.
- RIGHT(): Returns a specified number of characters from the end of a string.
- MID(): Extracts a substring from the middle of a string. The MID() function is a synonym for SUBSTRING().
- LOCATE(): Finds the position of a substring within a string.
- POSITION(): Finds the position of a substring. The
POSITION()is a synonym for theLOCATE()function. - INSTR(): Another function for finding the position of a substring.
- REPLACE(): Replaces all occurrences of a substring in a string.
- TRIM(): Removes leading and trailing spaces from a string.
- LTRIM(): Removes leading spaces from a string.
- RTRIM(): Removes trailing spaces from a string.
- REPEAT(): Repeats a string a specified number of times.
- REVERSE(): Reverses the characters in a string.
- INSERT(): Replaces a substring within a string with a new substring.
- SPACE(): Returns a string consisting of spaces.
- ASCII(): Returns the ASCII value of the leftmost character of a string.
- CHAR(): Converts an ASCII value to a character.
- LENGTH(): Returns the length of a string in bytes.
- CHAR_LENGTH(): Returns the length of a string in characters.
- OCTET_LENGTH(): Returns the length of a string in bytes.
- BIT_LENGTH(): Returns the length of a string in bits.
- CHARACTER_LENGTH(): Returns the length of a string in characters.
- BIT_COUNT(): Counts the number of bits in a binary string.
- STRCMP(): Compares two strings and returns their relative order.