存储过程中的动态sql

Question

I would like to pass in a dynamic column name to calculate its standard deviation,in oracle, the following is the code:

CREATE OR REPLACE 
PROCEDURE ReportCalculate
  (
    param_columnName IN VARCHAR2 DEFAULT 'COMPUTED_CP_MLIFTOFF_KNOT9OR10'
)
  AS 
  sqlstr VARCHAR2(500);
  result NUMBER;
  BEGIN
    sqlstr:='select stddev(:col) from LIDISUDUXIAO where 1=1 and NO_10_LIMITSIGN_DEPART_ID<>0';
    execute immediate sqlstr into result using param_columnName;
    DBMS_OUTPUT.PUT_LINE(result);
  END;

I call it with the default parameters,the error message is:

Procedure execution failed
ORA-01722: invalid number
ORA-06512: at "AGS.REPORTCALCULATE", line 10
ORA-06512: at line 1

How can i solve it?

Answer 1

A column name cannot be used as parameter of a query. You need to edit the sqlstr variable to include the provided param_columnName in the query itself before executing it:

CREATE OR REPLACE 
PROCEDURE ReportCalculate
  (
    param_columnName IN VARCHAR2 DEFAULT 'COMPUTED_CP_MLIFTOFF_KNOT9OR10'
)
  AS 
  sqlstr VARCHAR2(500);
  result NUMBER;
  BEGIN
    sqlstr:='select stddev(' || param_columnName || ') from LIDISUDUXIAO where 1=1 and NO_10_LIMITSIGN_DEPART_ID<>0';
    execute immediate sqlstr into result;
    DBMS_OUTPUT.PUT_LINE(result);
  END;