Oracle database, built-in function summary

1. Aggregation function

Count (field)         //number of non-empty lines max (field)            //Get maximum sum (field)              //Sum avg (field)/               /   average min (field)             /   min value

2. Conversion function

To_date ()       string-to-time  format: to_date (String, ' Yyyy-mm-dd hh24:mi:ss ') Example: To_date   (' 1970-1-1 15:31:33 '  ,   ' Yyyy-mm-dd   Hh24:mi:  SS  ') To_char ()     time-to-string format: To_char (a time, ' yyyy-mm-dd ') Example: To_char (Sbirthday, ' Yyyy-mm-dd '   ) cast ()       General conversion function format: CAST (data as data type (length)) Example: Cast (' 123456 ' as char (6)   )                                             //converted from a string to a number

3. Time function

Sysdate//                                                                                         system Current time add_mouthe (time, value)                                                                           //month plus minus last_day ()                                                                                  //Last day of the current month

4. String functions

Length (string or field name)                                                       //Get string    trim (string or field name)                                                         //Get string, remove front and back space before plus L is remove left space   ltrim (), front plus R is remove right space   RTrim () Replace (field name, '  )                                                           //Find and replace (go space) replace (data, ' Find string ',   ' new string ')                        //Replace substr (string, start position)                                                            //intercept field, default intercept to last Substr (string, start position, end position)                                     //default intercept to specified position                                         //If start position <0, calculate position from right start            InStr (Data, ' Find string ')                                           //Find string and return first position, not found return 0

5. Numerical functions

ABS ()/                                                                                             /Get Absolute mod ()                                                                                             //round (value)/////                                                                           /////  By default, rounding round (number, number of digits)//number of digits >0 the number of digits  after the decimal point =0  Rounding, number of digits <0 the   decimal point before rounding ceil () upper bound value                                                                              //greater than or equal to its smallest integer floor () lower value                                                                        //less than equals to his smallest integer trunc () direct intercept integer//                                                        number of digits >0  The number of digits after the decimal point, the number of digits =0 rounding  , the number of digits <0 the   decimal point before rounding

　　

6. Replace function

NVL (value, default)                                                 //Replace null value with default value nv12 (field, non-null replacement value, default value)                                    //replace NULL with default value, change non-null to new value decode (field, value 1, replace value 1, value 2, replace value 2 ....) Default value)                 //Match the value of the field and replace the new value

　　

Oracle database, built-in function summary