How can I create a table with a dynamic name (based on current_date) and reference to it in INSERT statements?

问题

At the moment I have to rerun data selection query every month, where I create one base table. This table is named something like MyDB.MyTable_Current_Date, so for today that would be MyDB.MyTable_201811 using YYYYMM date format.

Instead of having to set the name manually (using ctrl + h), I would like this to be done automaticaly. My goal is that I can open the SQL and run the query where the the table that is created is MyTable_YYYYMM.

Note: eventually I want to also let the SQL run automatically every month, but for now this is a nice first step for my understanding.

I made the below stored procedure. The problem is that if I want to do an alter table or insert into statement, I cannot (or don't know how to) refer to the table that was created.

REPLACE PROCEDURE DB.table_yymm
(
IN      db_name VARCHAR(128), 
    tbl_name    VARCHAR(128)
    )
BEGIN
    DECLARE create_name VARCHAR(261) 
    ;   
    DECLARE sql_stmt    VARCHAR(600)
    ;

    SET create_name = db_name || '.' || tbl_name || CAST(
                                                    (CURRENT_DATE (FORMAT 'yymm'))
                                                    AS CHAR(4)
                                                    )
    ;
    SET sql_stmt = 'CREATE TABLE ' || create_name || ' (testvar char(1))' || ';' ;

    EXECUTE IMMEDIATE sql_stmt;         
END;

CALL prd_work_lm.table_yymm('My_DB', 'My_Table')

Should I do this using a stored procedure, or using a user defined function?

It would be ideal if I could simply refer to some function, for example: CREATE TABLE DB.My_UDF(<My_DB>, <My_Table_Name>)

Could you help me by providing an example of a code sample?

回答1:

Instead of initially creating the new table MyDB.MyTable_201811 and use it throughout your script you can simply create a table with a known name, e.g. MyDB.MyTable_000000. Now this name is used and renamed as last step.

This is a slight variation of an existing SP to rename a table from '..._000000' to '..._yyyymmdd':

REPLACE PROCEDURE rename_table_to_yyyymm
(
  IN db_name VARCHAR(128) CHARACTER SET Unicode,
  IN tbl_name VARCHAR(128) CHARACTER SET Unicode,
  OUT msg VARCHAR(600) CHARACTER SET Unicode
) SQL SECURITY INVOKER
BEGIN
   DECLARE old_name VARCHAR(261)  CHARACTER SET Unicode;
   DECLARE new_name VARCHAR(261)  CHARACTER SET Unicode;

   DECLARE sql_stmt VARCHAR(600)  CHARACTER SET Unicode;

   SET old_name  = '"' || Coalesce(NullIf(db_name,''), DATABASE) || '"."' 
                       || Coalesce(tbl_name, '') || '"';

   SET new_name  = '"' || Coalesce(NullIf(db_name,''),DATABASE) || '"."' 
                       || Trim(Trailing '0' FROM tbl_name)-- remove '000000' at the end of the table name
                       || '_' || To_Char(Current_Date, 'YYYYMM') || '"';

   SET sql_stmt = 'RENAME TABLE ' || old_name || ' AS ' || new_name || ';'; 

   EXECUTE IMMEDIATE sql_stmt;

   SET msg = ' Table ' || old_name || ' renamed to ' || new_name;

END;

来源：https://stackoverflow.com/questions/53297953/how-can-i-create-a-table-with-a-dynamic-name-based-on-current-date-and-referen

标签

sql

function

stored-procedures

teradata