function.txt

在windows平台下

  REPLACE(str,from_str,to_str)|Returns the string str with all all occurrences of the string from_str replaced by the string to_str.
  REVERSE(str)|Returns the string str with the order of the characters reversed.
  RIGHT(str,len)|Returns the rightmost len characters from the string str.
  RPAD(str,len,padstr)|Returns the string str, right-padded with the string padstr until str is len characters long.
  RTRIM(str)|Returns the string str with trailing space characters removed.
  SOUNDEX(str)|Returns a soundex string from str. Two strings that sound "about the same" should have identical soundex strings.
  SPACE(N)|Returns a string consisting of N space characters.
  SUBSTRING(str,pos,len)|Returns a substring len characters long from string str, starting at position pos.
  SUBSTRING_INDEX(str,delim,count)|Returns the substring from string str before count occurrences of the delimiter delim.
  TRIM([[BOTH | LEADING | TRAILING] [remstr] FROM] str)|Returns the string str with all remstr prefixes and/or suffixes removed. If none of the specifiers BOTH, LEADING or TRAILING are given, BOTH is assumed.
  UCASE(str)|Returns the string str with all characters changed to uppercase according to the current character set mapping (the default is ISO-8859-1 Latin1).
  UPPER(str)|Returns the string str with all characters changed to uppercase according to the current character set mapping (the default is ISO-8859-1 Latin1).
Date and Time
  ADDDATE(date,INTERVAL expr type)|Performs date arithmetic.
  CURDATE()|Returns today's date as a value in "YYYY-MM-DD" or YYYYMMDD format, depending on whether the function is used in a string or numeric context.
  CURTIME()|Returns the current time as a value in "HH:MM:SS" or HHMMSS format, depending on whether the function is used in a string or numeric context.
  DATE_ADD(date,INTERVAL expr type)|Performs date arithmetic.
  DATE_FORMAT(date,format)|Formats the date value according to the format string.
  DATE_SUB(date,INTERVAL expr type)|Performs date arithmetic.
  DAYNAME(date)|Returns the name of the weekday for date.
  DAYOFMONTH(date)|Returns the day of the month for date, in the range 1 to 31.
  DAYOFWEEK(date)|Returns the weekday index for date (1 = Sunday, 2 = Monday, ... 7 = Saturday). These index values correspond to the ODBC standard.
  DAYOFYEAR(date)|Returns the day of the year for date, in the range 1 to 366.
  EXTRACT
  FROM_DAYS(N)|Given a daynumber N, returns a DATE value.
  FROM_UNIXTIME(unix_timestamp,format)|Returns a representation of the unix_timestamp argument as a value in "YYYY-MM-DD HH:MM:SS" or YYYYMMDDHHMMSS format, depending on whether the function is used in a string or numeric context.
  HOUR(time)|Returns the hour for time, in the range 0 to 23.
  MINUTE(time)|Returns the minute for time, in the range 0 to 59.
  MONTH(date)|Returns the month for date, in the range 1 to 12.
  MONTHNAME(date)|Returns the name of the month for date.
  NOW()|Returns the current date and time as a value in "YYYY-MM-DD HH:MM:SS" or YYYYMMDDHHMMSS format, depending on whether the function is used in a string or numeric context.
  PERIOD_ADD(P,N)|Adds N months to period P (in the format YYMM or YYYYMM). Returns a value in the format YYYYMM.
  PERIOD_DIFF(P1,P2)|Returns the number of months between periods P1 and P2. P1 and P2 should be in the format YYMM or YYYYMM.
  QUARTER(date)|Returns the quarter of the year for date, in the range 1 to 4.
  SECOND(time)|Returns the minute for time, in the range 0 to 59.
  SEC_TO_TIME(seconds)|Returns the seconds argument, converted to hours, minutes and seconds, as a value in "HH:MM:SS" or HHMMSS format, depending on whether the function is used in a string or numeric context.
  SUBDATE(date,INTERVAL expr type)|Performs date arithmetic.
  SYSDATE()|Returns the current date and time as a value in "YYYY-MM-DD HH:MM:SS" or YYYYMMDDHHMMSS format, depending on whether the function is used in a string or numeric context.
  TIME_FORMAT(time,format)|This is used like the DATE_FORMAT() function above, but the format string may contain only those format specifiers that handle hours, minutes and seconds.
  TIME_TO_SEC(time)|Returns the time argument, converted to seconds.
  TO_DAYS(date)|Given a date date, returns a daynumber (the number of days since year 0).
  UNIX_TIMESTAMP(date)|If called with no argument, returns a Unix timestamp (seconds since "1970-01-01 00:00:00" GMT). If UNIX_TIMESTAMP() is called with a date argument, it returns the value of the argument as seconds since "1970-01-01 00:00:00" GMT.
  WEEK(date)|With a single argument, returns the week for date, in the range 0 to 53
  WEEKDAY(date)|Returns the weekday index for date (0 = Monday, 1 = Tuesday, ... 6 = Sunday).
  YEAR(date)|Returns the year for date, in the range 1000 to 9999.
  YEARWEEK(date,first)|Returns year and week for a date. The second arguments works exactly like the second argument to WEEK().
Summarizing
  AVG(expr)|Returns the average value of expr.
  BIT_AND(expr)|Returns the bitwise AND of all bits in expr. The calculation is performed with 64-bit (BIGINT precision).
  BIT_OR(expr)|Returns the bitwise OR of all bits in expr. The calculation is performed with 64-bit (BIGINT precision).
  COUNT(expr)|Returns a count of the number of non-NULL values in the rows retrieved by a SELECT statement.
  MAX(expr)|Returns the maximum value of expr. May take a string argument; in such cases it returns the maximum string value.
  MIN(expr)|Returns the minimum value of expr. May take a string argument; in such cases it returns the minimum string value.
  STD(expr)|Returns the standard deviation of expr. This is an extension to ANSI SQL. The STDDEV() form of this function is provided for Oracle compatability.
  STDDEV(expr)|Returns the standard deviation of expr. This is an extension to ANSI SQL. The STDDEV() form of this function is provided for Oracle compatability.
  SUM(expr)|Returns the sum of expr. Note that if the return set has no rows, it returns NULL!
Miscellaneous
  BENCHMARK(count,expr)|Executes the expression expr repeatedly count times. It may be used to time how fast MySQL processes the expression.
  BIT_COUNT(N)|Returns the number of bits that are set in the argument N.
  CONNECTION_ID()|Returns the connection id (thread_id) for the connection. Every connection has its own unique id.
  DATABASE()|Returns the current database name.
  DECODE(crypt_str,pass_str)|Descrypts the encrypted string crypt_str using pass_str as the password. crypt_str should be a string returned from ENCODE().
  ENCODE(str,pass_str)|Encrypt str using pass_str as the password. To decrypt the result, use DECODE(). The results is a binary string of the same length as string. If you want to save it in a column, use a BLOB column type.
  ENCRYPT(str[,salt])|Encrypt str using the Unix crypt() system call. The salt argument should be a string with two characters. (As of MySQL 3.22.16, salt may be longer than two characters.)
  GET_LOCK(str,timeout)|Tries to obtain a lock with a name given by the string str, with a timeout of timeout seconds. Returns 1 if the lock was obtained successfully, 0 if the attempt timed out, or NULL if an error occurred (such as running out of memory or the thread was killed with mysqladmin kill).
  INET_NTOA(expr)|Returns the network address (4 or 8 byte) for the numeric expression.
  INET_ATON(expr)|Returns an integer that represents the numeric value for a network address Addresses may be 4 or 8 byte addresses.
  LAST_INSERT_ID([expr])|Returns the last automatically generated value that was inserted into an AUTO_INCREMENT column.
  LOAD_FILE(file_name)|Reads the file and returns the file contents as a string. The file must be on the server, you must specify the full pathname to the file, and you must have the file privilege.
  MD5(string)|Calculates a MD5 checksum for the string. Value is returned as a 32 long hex number that may, for example, be used as a hash key.
  PASSWORD(str)|Calculates a password string from the plaintext password str. This is the function that is used for encrypting MySQL passwords for storage in the Password column of the user grant table.
  RELEASE_LOCK(str)|Releases the lock named by the string str that was obtained with GET_LOCK(). Returns 1 if the lock was released, 0 if the lock wasn't locked by this thread (in which case the lock is not released) and NULL if the named lock didn't exist.
  SESSION_USER()|Returns the current MySQL user name.
  SYSTEM_USER()|Returns the current MySQL user name.
  USER()|Returns the current MySQL user name.
  VERSION()|Returns a string indicating the MySQL server version.