Example: LAG with IGNORE NULLS

Teradata Vantageā„¢ SQL Functions, Expressions, and Predicates

brand
Software
Teradata Vantage
prodname
Teradata Database
Teradata Vantage NewSQL Engine
vrm_release
16.20
category
Programming Reference
featnum
B035-1145-162K

ANSI style syntax:

SELECT empno, empname, job, sal, 
       LAG(sal, 1, 0) IGNORE NULLS 
       OVER (PARTITION BY job ORDER BY empno) AS sal_prev 
FROM   emp
ORDER BY job, empno;

 EMPNO      EMPNAME      JOB       SAL      SAL_PREV
---------- ---------- --------- ---------- ----------
   12        PAUL       ANALYST    ?          0
   13        GRACE      ANALYST    3000       0
   1         JOHN       CLERK      800        0
   2         ERIC       CLERK      950        800
   3         KURT       CLERK      ?          950
   6         JULIE      CLERK      1300       950
   9         NICHOLAS   MANAGER    2450       0
   10        NOVAK      MANAGER    ?          2450
   11        ROGER      MANAGER    2850       2450
   14        RICH       PRESIDENT  5000       0
   4         KENT       SALESMAN   1250       0
   5         LYNN       SALESMAN   ?          1250
   7         TERESA     SALESMAN   1500       1250
   8         MATTHEW    SALESMAN   1600       1500

Teradata style syntax:

SELECT empno, empname, job, sal, 
       LAG(sal IGNORE NULLS, 1, 0)  
       OVER (PARTITION BY job ORDER BY empno) AS sal_prev 
FROM   emp
ORDER BY job, empno;

 EMPNO      EMPNAME      JOB       SAL      SAL_PREV
---------- ---------- --------- ---------- ----------
   12        PAUL       ANALYST    ?          0
   13        GRACE      ANALYST    3000       0
   1         JOHN       CLERK      800        0
   2         ERIC       CLERK      950        800
   3         KURT       CLERK      ?          950
   6         JULIE      CLERK      1300       950
   9         NICHOLAS   MANAGER    2450       0
   10        NOVAK      MANAGER    ?          2450
   11        ROGER      MANAGER    2850       2450
   14        RICH       PRESIDENT  5000       0
   4         KENT       SALESMAN   1250       0
   5         LYNN       SALESMAN   ?          1250
   7         TERESA     SALESMAN   1500       1250
   8         MATTHEW    SALESMAN   1600       1500