The 11th chapter uses the data processing function

1. The portability of the function is not strong compared to the portability of SQL 2. The text-processing function left () returns the length of the string () () to return the string locate () to find the string of strings lower () to turn the string into lowercase ltrim () to remove the left space ritht () Returns the character to the right of the string RTrim () strips the right-hand space Soundex () returns the Soundex value of the string  

3. Date and time processing function adddate () adds a date adddate (date, INTERVAL expr unit), adddate (expr,days) The following table shows the expected form of the expr argument for each unit value.

Addtime () Add a time (hour, minute, etc)

Date_add () Date arithmetic function is equivalent to adddate () effect after using INTERVAL flag date_add (date, INTERVAL expr unit)

Date () returns the datetime time of Year () the Day of the month (s) to get the date

DayOfWeek () for a date to return its subscript for the day of the week, 1 indicates that the year of Sunday () gets the date of the month part of the return date () returns the date part of the hour () returns the date when part of the minute () returns the date of the clock part second () Gets the second part of the date

Note: The date format is best: "Yyyy-mm-dd", so as to avoid ambiguity 4. Numeric processing function ABS () returns the absolute value of the passed-in value cos () returns an angle of the cosine exp () returns the X-exponent of E after mod () returns the remainder of the action () Pi () return pi

RAND () returns a random value of sin () that returns a sine of an angle sqrt () returns a number of square root tan () that returns the tangent of a number

　　

The 11th chapter uses the data processing function