OCI要求选择语句

Question

I have to write OCI code for a simple query like Select * from emp;

Since I dont know how many rows will be returned I cannot preallocate my buffers So I define a void ** pointer while I associate my output buffers.

The idea is to call the OCIStmtExecute with iters = 0 since

For SELECT statements, if iters is nonzero, then defines must have been done for the statement handle. The execution fetches iters rows into these predefined buffers and prefetches more rows depending upon the prefetch row count. If you do not know how many rows the SELECT statement will retrieve, set iters to zero.

This function returns an error if iters=0 for non-SELECT statements.

After that I plan to do OCIAttrGet(OCI_ATTR_ROW_COUNT) to get the numbers to rows returned by the select statement and then allocate memory for the output buffers and then call the OCIStmtFetch by specifying the numbers of rows hence returned.

But the row count that I get is 0 every time even though there is data returned by the table.

Is there some flaw with my approach? Could you point out the flaw

Answer 1

You simply need to allocate space for one row, then call OCIStmtFetch2() repeatedly until you reach the end of the result set (which will give error code 1403). The prefetch happens into a buffer maintained by OCI itself, transparently to you, so this method is not inefficient.