编辑特定列上的 DB2 数据

Question

Thank you in advance for any help...I have to edit some data on my DB2 database - working with version 11. Basically I have a column with multiple entries that look like this: <GUID=b92c4c2340953g98hn298743n5634234> and I need them to look like this: b92c4c23-4095-3g98-hn29-8743n5634234

Note** I am trying to create a function that takes in value A (<GUID=b92c4c2340953g98hn298743n5634234>) and returns value B (b92c4c23-4095-3g98-hn29-8743n5634234)

Answer 1

Use substring function SUBSTR as follows:

SUBSTR(SUBSTR(your_column, 1, LENGTH(your_column) - 1), 7)

Answer 2

Example:

with t(s) as ( 
    values '<GUID=b92c4c2340953g98hn298743n5634234>' 
), strip(s) as (
    select substr(s,7,length(s)-7) from t
) 
select substr(s,1,8) || '-' || substr(s,9,4) || '-' || substr(s,13,4) || '-' 
    || substr(s,17,4) || '-' || substr(s,21) 
from strip;

1                                                              
---------------------------------------------------------------
b92c4c23-4095-3g98-hn29-8743n5634234                           

If you do this a lot you may want to create a function:

create function trim_guid(s varchar(39)) 
returns varchar(36) 
    return with strip(s) as (
                values substr(s,7,length(s)-7)
           ) select substr(s,1,8) || '-' || substr(s,9,4) || '-' 
                 || substr(s,13,4) || '-' || substr(s,17,4) || '-' 
                 || substr(s,21) from strip


with t(s) as ( values '<GUID=b92c4c2340953g98hn298743n5634234>' ) 
select trim_guid(s) from t

1                                   
------------------------------------
b92c4c23-4095-3g98-hn29-8743n5634234

Answer 3

Db2 has some built in facilities for working with GUID values. There are functions to convert them to/from binary and character representations.

If your data are valid GUIDs, you can use the following for example to return a character GUID representation.

VALUES
    VARCHAR_FORMAT_BIT(
        CAST(HEXTORAW(SUBSTR('<GUID=d83d6360181811db9804b622a1ef5492>',7,32)) AS CHAR(16) FOR BIT DATA)
    ,   'xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx'
    )

will return

d83d6360-1818-11db-9804-b622a1ef5492

Needless to say, storing the data as BINARY(16) (aka CHAR(16) FOR BIT DATA ) is typically more efficient than using eg VARCHAR(32) . Still if GUIDs themselves are less efficient (from a database point of view) than eg integer sequence identifers.