SQL query to get previous and new column detail from a table - sql

Question

I have a table that has both audit data for addresses-
ADDRESS_ID EFFECTIVE_START_DATE EFFECTIVE_END_DATE ADDRESS_LINE_1 ADDRESS_LINE_2 TOWN Person_id
300000009360612 2020-04-01 4712-12-31 Box 14 ADAM SELLERS ST Mirror 157
300000009360612 2000-03-27 2020-03-31 Box 13 Mirror 157
I want the previous value and current value for the columns that change. For example, the output should look like -
ADDRESS_ID Changed Attribute Previous_Value Current_Value
300000009360612 Effective_start_Date 2000-03-27 2020-04-01
300000009360612 Effective_end_Date 2020-03-31 4712-12-31
300000009360612 ADDRESS_LINE_1 Box 13 Box 14
300000009360612 ADDRESS_LINE_2 ADAM SELLERS ST
I have tried -
select * from (
SELECT
address_id ,
'Effective_Start_Date' Changed_Attribute ,
cast(Effective_Start_Date as varchar(40)) current_value
, LAG(cast(effective_start_date as varchar(40)), 1, 0) OVER (partition by address_ID, effective_start_date ORDER BY last_update_date) Previous_Value
FROM fusion.per_addresses_f_
ORDER BY last_update_date DESC)
where current_value <> Previous_Value
The above query is not giving the right output. It is giving me the below output-
address_id Changed_Attribute current_value Previous_Value
300000009360612 Effective_start_Date 2020-04-01
i.e. i am not getting any value in previous_value.

Answer 1

select *
from (SELECT address_id,
'Effective_Start_Date' Changed_Attribute,
to_char(Effective_Start_Date, 'yyyy-mm-dd') current_value,
to_char(LAG(t.effective_start_date, 1) over(order by t.effective_start_date desc) , 'yyyy-mm-dd') Previous_Value
FROM AUDIT_DATA t
union all
SELECT address_id,
'Effective_end_Date' Changed_Attribute,
to_char(t.effective_end_date , 'yyyy-mm-dd') current_value,
to_char(LAG(t.effective_end_date, 1) over(order by t.effective_end_date desc) , 'yyyy-mm-dd') Previous_Value
FROM AUDIT_DATA t
union all
SELECT address_id,
'ADDRESS_LINE_1' Changed_Attribute,
t.address_line_1 current_value,
LAG(t.address_line_1, 1) over(order by t.address_line_1 desc) Previous_Value
FROM AUDIT_DATA t
union all
SELECT address_id,
'ADDRESS_LINE_2' Changed_Attribute,
Nvl(t.address_line_2, ' ') current_value,
LAG(t.address_line_2, 1) over(order by t.address_line_2) Previous_Value
FROM AUDIT_DATA t
) r
where Previous_Value <> current_value;

Answer 2

u can use ROW_NUMBER instead of LAG =
select * from (select address_id ,
'Effective_Start_Date' Changed_Attribute ,
cast(Effective_Start_Date as varchar(40)) current_value,
ROW_NUMBER() over(partition by address_ID order by last_update_date desc) as ROW_NO from fusion.per_addresses_f_ ) Q where q.ROW_NO=1 -- first of each partiotion = Previous_Value
....

Answer 3

You can generate the 6 rows for each ADDRESS and compare it as follows:
WITH CTE AS
(SELECT T.*,
ROW_NUMBER() OVER (PARTITION BY ADDRESS_ID ORDER BY EFFECTIVE_START_DATE DESC) AS RN
FROM YOUR_TABLE T)
SELECT * FROM
(SELECT TNEW.ADDRESS_ID,
DECODE(LVL,1,'Effective_start_Date',2,'Effective_end_Date',3,'ADDRESS_LINE_1',4,'ADDRESS_LINE_2',5,'TOWN') AS CHANGED_aTTRIBUTE,
DECODE(LVL,1,TOLD.Effective_start_Date,2,TOLD.Effective_end_Date,3,TOLD.ADDRESS_LINE_1,4,TOLD.ADDRESS_LINE_2,5,TOLD.TOWN) AS PREV_VALUE,
DECODE(LVL,1,TNEW.Effective_start_Date,2,TNEW.Effective_end_Date,3,TNEW.ADDRESS_LINE_1,4,TNEW.ADDRESS_LINE_2,5,TNEW.TOWN) AS CURRENT_VALUE
FROM CTE TNEW
JOIN CTE TOLD ON TNEW.ADDRESS_ID = TOLD.ADDRESS_ID AND TNEW.RN = 1 AND TOLD.RN=2
cross join (SELECT LEVEL AS LVL FROM DUAL CONNECT BY LEVEL <=5) L)
WHERE PREV_VALUE <> CURRENT_VALUE
OR (PREV_VALUE IS NULL AND CURRENT_VALUE IS NOT NULL)
OR (PREV_VALUE IS NOT NULL AND CURRENT_VALUE IS NULL)

Answer 4

Using the last_update_date to decide which record is the first one...
/*
ADDRESS_ID EFFECTIVE_START_DATE EFFECTIVE_END_DATE ADDRESS_LINE_1 ADDRESS_LINE_2 TOWN Person_id LAST_UPDATE_DATE
300000009360612 2020-04-01 4712-12-31 Box 14 ADAM SELLERS ST Mirror 157 2002-01-01
300000009360612 2000-03-27 2020-03-31 Box 13 Mirror 157 2002-02-02
*/
With a1 as (
select
cast('300000009360612' as varchar2(200)) as address_id
, cast('2020-04-01' as varchar2(200)) as EFFECTIVE_START_DATE
, cast('4712-12-31' as varchar2(200)) as EFFECTIVE_END_DATE
, cast('Box 14' as varchar2(200)) as ADDRESS_LINE_1
, cast('ADAM SELLERS ST' as varchar2(200)) as ADDRESS_LINE_2
, cast('Mirror' as varchar2(200)) as TOWN
, cast(157 as number(10)) as PERSON_ID
, to_date('2020-01-01', 'YYYY-MM-DD') as LAST_UPDATE_DATE
from dual
union all
select
'300000009360612', '2000-03-27', '2020-03-31', 'Box 13', NULL, 'Mirror', 157, to_date('2020-02-02', 'YYYY-MM-DD')
from dual
),
Q0 as (
select
address_id
, effective_start_date, effective_end_date
, address_line_1, address_line_2
, town, person_id
, effective_start_date as current_value
, LAG(effective_start_date, 1, 0) OVER (partition by person_id, address_id ORDER BY last_update_date) Previous_Value
from a1
),
Q1 as (
select
t1.address_id as address_id,
t1.effective_start_date as effective_start_date_t1, t2.effective_start_date as effective_start_date_t2,
t1.effective_end_date as effective_end_date_t1, t2.effective_end_date as effective_end_date_t2,
t1.address_line_1 as address_line_1_t1, t2.address_line_1 as address_line_1_t2,
t1.address_line_2 as address_line_2_t1, t2.address_line_2 as address_line_2_t2,
t1.town as town_t1, t2.town as town_t2,
to_char(t1.person_id) as person_id_t1, to_char(t2.person_id) as person_id_t2
, to_char(t1.last_update_date, 'YYYY-MM-DD') as last_update_date_t1, to_char(t2.last_update_date, 'YYYY-MM-DD') as last_update_date_t2
from a1 t1 inner join a1 t2 on (t1.person_id = t2.person_id and t1.address_id = t2.address_id and t1.LAST_UPDATE_DATE < t2.LAST_UPDATE_DATE)
where 1=1
order by t1.person_id, t1.address_id, t1.last_update_date
)
select
ADDRESS_ID
, COLX
, VAL1
, VAL2
--, case when nvl(VAL1, 'NA') != nvl(VAL2,'NA') THEN 1 ELSE 0 END CHANGED
from q1
unpivot (
(val1, val2)
for colx in (
(EFFECTIVE_START_DATE_T1, EFFECTIVE_START_DATE_T2) as 'EFFECTIVE_START_DATE'
, (EFFECTIVE_END_DATE_T1, EFFECTIVE_END_DATE_T2) as 'EFFECTIVE_END_DATE'
, (ADDRESS_LINE_1_T1, ADDRESS_LINE_1_T2) as 'ADDRESS_LINE_1'
, (ADDRESS_LINE_2_T1, ADDRESS_LINE_2_T2) as 'ADDRESS_LINE_2'
, (TOWN_T1, TOWN_T2) as 'TOWN'
, (PERSON_ID_T1, PERSON_ID_T2) as 'PERSON_ID'
, (LAST_UPDATE_DATE_T1, LAST_UPDATE_DATE_T2) as 'LAST_UPDATE_DATE'
)
)
where 1=1
and case when nvl(VAL1, 'NA') != nvl(VAL2,'NA') THEN 1 ELSE 0 END != 0
;
gives
ADDRESS_ID COLX VAL1 VAL2
300000009360612 EFFECTIVE_START_DATE 2020-04-01 2000-03-27
300000009360612 EFFECTIVE_END_DATE 4712-12-31 2020-03-31
300000009360612 ADDRESS_LINE_1 Box 14 Box 13
300000009360612 ADDRESS_LINE_2 ADAM SELLERS ST
300000009360612 LAST_UPDATE_DATE 2020-01-01 2020-02-02
NOTE: VAL1 = Previous Value and VAL2 = Current Value (based on LAST_UPDATE_DATE)