LAG() and LEAD(): get a value in a row where that row is a certain number of rows away from the current row : LAG LEAD « Analytical Functions « Oracle PL / SQL

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Oracle PL / SQL » Analytical Functions » LAG LEAD 
LAG() and LEAD(): get a value in a row where that row is a certain number of rows away from the current row



SQL> CREATE TABLE all_sales (
  2    year INTEGER,
  3    month INTEGER,
  4    prd_type_id INTEGER,
  5    emp_id INTEGER ,
  6    amount NUMBER(82)
  7  );

Table created.

SQL>
SQL> insert into all_sales (YEAR,MONTH,PRD_TYPE_ID,EMP_ID,AMOUNT)
  2                  values(2006,1    ,1          ,21    ,16034.84);

row created.

SQL> insert into all_sales (YEAR,MONTH,PRD_TYPE_ID,EMP_ID,AMOUNT)
  2                  values(2006,2    ,1          ,21    ,15644.65);

row created.

SQL> insert into all_sales (YEAR,MONTH,PRD_TYPE_ID,EMP_ID,AMOUNT)
  2                  values(2006,3    ,2          ,21    ,20167.83);

row created.

SQL> insert into all_sales (YEAR,MONTH,PRD_TYPE_ID,EMP_ID,AMOUNT)
  2                  values(2006,4    ,2          ,21    ,25056.45);

row created.

SQL> insert into all_sales (YEAR,MONTH,PRD_TYPE_ID,EMP_ID,AMOUNT)
  2                  values(2006,5    ,2          ,21    ,NULL);

row created.

SQL> insert into all_sales (YEAR,MONTH,PRD_TYPE_ID,EMP_ID,AMOUNT)
  2                  values(2006,6    ,1          ,21    ,15564.66);

row created.

SQL> insert into all_sales (YEAR,MONTH,PRD_TYPE_ID,EMP_ID,AMOUNT)
  2                  values(2006,7    ,1          ,21    ,15644.65);

row created.

SQL> insert into all_sales (YEAR,MONTH,PRD_TYPE_ID,EMP_ID,AMOUNT)
  2                  values(2006,8    ,1          ,21    ,16434.82);

row created.

SQL> insert into all_sales (YEAR,MONTH,PRD_TYPE_ID,EMP_ID,AMOUNT)
  2                  values(2006,9    ,1          ,21    ,19654.57);

row created.

SQL> insert into all_sales (YEAR,MONTH,PRD_TYPE_ID,EMP_ID,AMOUNT)
  2                  values(2006,10   ,1          ,21    ,21764.19);

row created.

SQL> insert into all_sales (YEAR,MONTH,PRD_TYPE_ID,EMP_ID,AMOUNT)
  2                  values(2006,11   ,1          ,21    ,13026.73);

row created.

SQL> insert into all_sales (YEAR,MONTH,PRD_TYPE_ID,EMP_ID,AMOUNT)
  2                  values(2006,12   ,2          ,21    ,10034.64);

row created.

SQL> insert into all_sales (YEAR,MONTH,PRD_TYPE_ID,EMP_ID,AMOUNT)
  2                  values(2005,1    ,2          ,22    ,16634.84);

row created.

SQL> insert into all_sales (YEAR,MONTH,PRD_TYPE_ID,EMP_ID,AMOUNT)
  2                  values(2005,1    ,2          ,21    ,26034.84);

row created.

SQL> insert into all_sales (YEAR,MONTH,PRD_TYPE_ID,EMP_ID,AMOUNT)
  2                  values(2005,2    ,1          ,21    ,12644.65);

row created.

SQL> insert into all_sales (YEAR,MONTH,PRD_TYPE_ID,EMP_ID,AMOUNT)
  2                  values(2005,3    ,1          ,21    ,NULL);

row created.

SQL> insert into all_sales (YEAR,MONTH,PRD_TYPE_ID,EMP_ID,AMOUNT)
  2                  values(2005,4    ,1          ,21    ,25026.45);

row created.

SQL> insert into all_sales (YEAR,MONTH,PRD_TYPE_ID,EMP_ID,AMOUNT)
  2                  values(2005,5    ,1          ,21    ,17212.66);

row created.

SQL> insert into all_sales (YEAR,MONTH,PRD_TYPE_ID,EMP_ID,AMOUNT)
  2                  values(2005,6    ,1          ,21    ,15564.26);

row created.

SQL> insert into all_sales (YEAR,MONTH,PRD_TYPE_ID,EMP_ID,AMOUNT)
  2                  values(2005,7    ,2          ,21    ,62654.82);

row created.

SQL> insert into all_sales (YEAR,MONTH,PRD_TYPE_ID,EMP_ID,AMOUNT)
  2                  values(2005,8    ,2          ,21    ,26434.82);

row created.

SQL> insert into all_sales (YEAR,MONTH,PRD_TYPE_ID,EMP_ID,AMOUNT)
  2                  values(2005,9    ,2          ,21    ,15644.65);

row created.

SQL> insert into all_sales (YEAR,MONTH,PRD_TYPE_ID,EMP_ID,AMOUNT)
  2                  values(2005,10   ,2          ,21    ,21264.19);

row created.

SQL> insert into all_sales (YEAR,MONTH,PRD_TYPE_ID,EMP_ID,AMOUNT)
  2                  values(2005,11   ,1          ,21    ,13026.73);

row created.

SQL> insert into all_sales (YEAR,MONTH,PRD_TYPE_ID,EMP_ID,AMOUNT)
  2                  values(2005,12   ,1          ,21    ,10032.64);

row created.

SQL>
SQL> select from all_sales;

      YEAR      MONTH PRD_TYPE_ID     EMP_ID     AMOUNT
---------- ---------- ----------- ---------- ----------
      2006          1           1         21   16034.84
      2006          2           1         21   15644.65
      2006          3           2         21   20167.83
      2006          4           2         21   25056.45
      2006          5           2         21
      2006          6           1         21   15564.66
      2006          7           1         21   15644.65
      2006          8           1         21   16434.82
      2006          9           1         21   19654.57
      2006         10           1         21   21764.19
      2006         11           1         21   13026.73
      2006         12           2         21   10034.64
      2005          1           2         22   16634.84
      2005          1           2         21   26034.84
      2005          2           1         21   12644.65
      2005          3           1         21
      2005          4           1         21   25026.45
      2005          5           1         21   17212.66
      2005          6           1         21   15564.26
      2005          7           2         21   62654.82
      2005          8           2         21   26434.82
      2005          9           2         21   15644.65
      2005         10           2         21   21264.19
      2005         11           1         21   13026.73
      2005         12           1         21   10032.64

25 rows selected.

SQL>
SQL> --LAG() and LEAD(): get a value in a row where that row is a certain number of rows away from the current row.
SQL>
SQL> --The following query uses LAG() and LEAD() to get the previous and next month’s sales amount:
SQL>
SQL> SELECT
  2   month, SUM(amountAS month_amount,
  3   LAG(SUM(amount)1OVER (ORDER BY monthAS previous_month_amount,
  4   LEAD(SUM(amount)1OVER (ORDER BY monthAS next_month_amount
  5  FROM all_sales
  6  GROUP BY month
  7  ORDER BY month;

     MONTH MONTH_AMOUNT PREVIOUS_MONTH_AMOUNT NEXT_MONTH_AMOUNT
---------- ------------ --------------------- -----------------
         1     58704.52                                 28289.3
         2      28289.3              58704.52          20167.83
         3     20167.83               28289.3           50082.9
         4      50082.9              20167.83          17212.66
         5     17212.66               50082.9          31128.92
         6     31128.92              17212.66          78299.47
         7     78299.47              31128.92          42869.64
         8     42869.64              78299.47          35299.22
         9     35299.22              42869.64          43028.38
        10     43028.38              35299.22          26053.46
        11     26053.46              43028.38          20067.28
        12     20067.28              26053.46

12 rows selected.

SQL>
SQL>
SQL>
SQL> drop table all_sales;

Table dropped.

SQL>
SQL>
           
       
Related examples in the same category
1. The Row Comparison Functions LEAD and LAG
2. The row comparison function can also be partitioned as with other aggregates
3. LAG, LEAD: allow specified offsets and default values for the nulls that result in non-applicable rows
4. lead over order by
5. Lag over
6. Lead over partition
7. Lag over order
8. Use lag over in inner query
9. Use lag over and lead over in inner statement
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