Obtain jagged rows

Jagged rows occur as a result of a query that uses the following syntax to request all the rows in a supertable and all its subtables:

SELECT correlation_variable 
FROM table_name correlation_variable;

In the preceding query, table_name represents a supertable in an inheritance hierarchy. Suppose you create the following schema in which the table parent has one column, child has two columns, and grandchild has three columns:

CREATE TABLE parent OF TYPE parent_t (num1 INTEGER);
INSERT INTO parent VALUES (10);

CREATE TABLE child OF TYPE child_t (num2 SMALLFLOAT) 
   UNDER parent;
INSERT INTO child VALUES (20, 3.5);

CREATE TABLE grandchild OF TYPE grandchild_t (name TEXT)
   UNDER child;
INSERT INTO grandchild VALUES (30, 7.8, 'gundrun');

The following SELECT statement queries the parent supertable:

SELECT p FROM parent p;

This query returns the following three jagged rows:

p (parent_t)
num1
10

p (child_t)
num1             num2
20               3.5E+00

p (grandchild_t)
num1             num2               name
30               7.8E+00            gundrun

The DataBlade® API indicates that a query returned a jagged row as follows:

• The mi_value() or mi_value_by_name() function returns a value status of MI_ROW_VALUE.
• The contents of the MI_DATUM structure that holds the retrieved column is a pointer to a row structure.

The format of the columns depends on whether the control mode for the query data is text or binary representation, as the following table shows.