OLAST - Teradata Database

OLAST

Purpose  

Returns the highest subscript value with a populated element in array_expr.

Syntax  

System function syntax:

Method-style syntax:

where:

Syntax element…	Specifies…
TD_SYSFNLIB	the name of the database where the method is located.
array_expr	an ARRAY expression, which is one of the following: A reference to an ARRAY column An ARRAY constructor expression. See “ARRAY Constructor Expression” on page 195. A UDF expression A UDM expression

ANSI Compliance

This is a Teradata extension to the ANSI SQL:2011 standard.

Usage Notes  

OLAST takes an array expression as an argument and returns the highest subscript value with a populated element in the ARRAY type. This is different from the highest possible subscript value, as returned by the OLIMIT method. If array_expr is a one-dimensional ARRAY type, OLAST returns an unsigned INTEGER value. If array_expr is a multidimensional ARRAY type, OLAST returns a new instance of the predefined ARRAY type ArrayVec, containing the subscript information. If the array is empty (all elements of the array are in an uninitialized state), then OLAST returns NULL.

If array_expr is NULL, an error is returned.

The OLAST method is compatible with the Oracle LAST method for one-dimensional ARRAY types. However, the empty set of parentheses required by Teradata syntax is a deviation from Oracle syntax.

Result Type

OLAST returns an unsigned INTEGER value or a new instance of the predefined ARRAY type ArrayVec.

Example  

Consider the following one-dimensional ARRAY data type and table.

CREATE TYPE phonenumbers AS VARRAY(20) OF CHAR(10);

CREATE TABLE employee_info (eno INTEGER, phonelist phonenumbers);

The table is populated with the following values:

/* The first 2 elements are populated; the rest are uninitialized. */

INSERT INTO employee_info VALUES (1, 

   phonenumbers('1112223333', '6195551234'));

/* Empty ARRAY instance */

INSERT INTO employee_info VALUES (2, 

   phonenumbers());

/* Update empty ARRAY instance such that element 3 is set to a value;

   Then elements 1 and 2 are set to NULL, the rest are uninitialized */

UPDATE employee_info

SET phonelist[3] = '8584850000'

WHERE id = 2;

The following query returns the highest subscript value with a populated element in the phonelist array.

SELECT eno, phonelist.OLAST()

FROM employee_info;

The following is the result of the query.

ENO         phonelist.OLAST()

---         -----------------

 1           2

 2           3

The following is the same query using function-style syntax.

SELECT eno, OLAST(phonelist) 

FROM employee_info;

Example  

Consider the following 2-D ARRAY data type and table.

CREATE TYPE shot_ary AS VARRAY(1:50)(1:50) OF INTEGER;

CREATE TABLE seismic_table (

   id INTEGER,

   shots shot_ary);

The table is populated with the following values:

/* The first 2 elements are populated; the rest are uninitialized. */

INSERT INTO seismic_table VALUES (1, shot_ary(11, 12));

/* Empty ARRAY instance */

INSERT INTO seismic_table VALUES (2, shot_ary());

/* Update empty ARRAY instance such that element [1][3] is set to a value; Then elements [1][1] and [1][2] are set to NULL, the rest are uninitialized */

UPDATE seismic_table

SET shots[1][3] = 1133

WHERE id = 2;

The following query returns the highest subscript value with a populated element in the shots array.

SELECT id, shots.OLAST()

FROM seismic_table;

The following is the result of the query.

ID          shots.OLAST()

--          ------------------

 1           NEW arrayVec(1,2)

 2           NEW arrayVec(1,3)