PL/SQL Cursor for loop | 易学教程

问题

I believe I need a cursor for loop to go through the street1 column from table test_data. I have a program which needs to test each row from the table.

This is what I have so far:

cursor c1 is
street1
from test_data

Begin
    If Instr(street1, ‘Cnr’, 1) >= 1;
    Then
        Newstreetname := Substr(street1, Instr(street1, ‘Cnr’, 1)+3);
    Else if
        Instr(street1, ‘PO Box’, 1) >= 1;
    Then
        Newstreetname:= Substr(street1, Instr(street1, ‘PO Box’, 1));
    Else if
        REGEXP_ Instr (street1, [\d], 1) = 0; 
    Then
        Newstreetname:= street1;
    Else if
        REGEXP_ Instr (street1, [\d], 1) >= 1;
    Then
        Newstreetnumber:= regexp_substr(street1, '\d+(\s|\/)(\d+)?-?(\d+)?(\w {1})?'); 
        Newstreetname:= regexp_substr(street1, '(\w+\s\w+)$'); 
End

回答1:

*1. You need a SELECT and a semicolon in the cursor definition

*2. You can add a FOR LOOP over the cursor

For example:

    DECLARE
      cursor c1 is
        SELECT street1
        from test_data;
      r1 c1%ROWTYPE;
    BEGIN
      FOR r1 IN c1 LOOP
         ... do your stuff with r1.street1
      END LOOP;
    END;

You can, alternatively, avoid the explicit cursor definition entirely, e.g.:

FOR r1 IN (SELECT street1 FROM test_data) LOOP
   ... do your stuff with r1.street1
END LOOP;

*3. Your IF statements cannot include a semicolon - e.g.:

    If
    Instr(r1.street1, 'Cnr', 1) >= 1
    Then

*4. [edit] so you want to update your table, columns newstreetnumber and newstreetname - in which case you could do something like this:

    DECLARE
      cursor c1 is
        SELECT street1
        from test_data
        FOR UPDATE;
      r1 c1%ROWTYPE;
    BEGIN
      FOR r1 IN c1 LOOP
         ... do your stuff with r1.street1
         UPDATE test_data
         SET newstreetnumber = ...
            ,newstreetname = ...
         WHERE CURRENT OF c1;
      END LOOP;
    END;

Note, however, that this will not perform well for large volumes, and I'd prefer to do it all in one UPDATE statement.

回答2:

As Jeffrey Kemp said this can be done in one update statemant:

UPDATE test_data
   SET newstreetname = CASE WHEN Instr(street1, ‘Cnr’, 1) >= 1 
                             THEN Substr(street1, Instr(street1, ‘Cnr’, 1)+3)
                            WHEN Instr(street1, ‘PO Box’, 1) >= 1 
                             THEN Substr(street1, Instr(street1, ‘PO Box’, 1))
                            WHEN REGEXP_Instr (street1, '[\d]', 1) = 0 
                             THEN street1
                            WHEN REGEXP_Instr (street1, '[\d]', 1) >= 1 
                             THEN regexp_substr(street1, '(\w+\s\w+)$')
                       END,
       newstreetnumber = CASE WHEN .....
                       END;

来源：https://stackoverflow.com/questions/10183061/pl-sql-cursor-for-loop

标签

Oracle

plsql

for-loop

cursor