如何在不丢失右表列中的值的情况下使用左连接添加其他列？

Question

Table A Country | Date | Source | Campaign | Leads (sum)

Table B Country | Date | Source | Campaign | Purchases (sum) | Revenue (sum)

SELECT
a.*,
b.purchases,
b.revenue

FROM
Table A 
LEFT JOIN 
Table B 

ON a.country = b.country and a.date = b.date and a.source = b.source and a.campaign = b.campaign

Desired Output:

Country | Date | Source | Campaign | Leads | Purchases | Revenue

When I do this, the total number of leads remain the same as in Table A but the total number of purchases and sum of revenue from Table B drops after the join. This should not be the case.

I'm not able to figure out why this would be the case - the idea is that not all campaign leads result in a purchase, hence the Left Join instead of Inner Join.

Update:

Table A

country times   sources camp    leads
Germany 01-Jan-20   Facebook    a   227
Germany 02-Jan-20   Facebook    b   175
Germany 03-Jan-20   Facebook    c   215
Germany 04-Jan-20   Facebook        23
Germany 05-Jan-20   Facebook        251
Germany 06-Jan-20   Facebook    d   135
Germany 07-Jan-20   Facebook        257
Germany 08-Jan-20   Facebook    e   54
Germany 09-Jan-20   Facebook        51
Germany 10-Jan-20   Facebook        27
Germany 11-Jan-20   Facebook        264
Germany 12-Jan-20   Facebook    f   41
Germany 13-Jan-20   Facebook        359
Germany 14-Jan-20   Facebook        2
Germany 15-Jan-20   Facebook    g   33

Table B

country times   sources camp    purchases   revenue
Germany 01-Jan-20   Facebook    a       
Germany 02-Jan-20   Facebook    b       
Germany 03-Jan-20   Facebook    c   1   127.88
Germany 04-Jan-20   Facebook        1   93.42
Germany 05-Jan-20   Facebook        1   74.18
Germany 06-Jan-20   Facebook    d       
Germany 07-Jan-20   Facebook            
Germany 08-Jan-20   Facebook    e       
Germany 09-Jan-20   Facebook            
Germany 10-Jan-20   Facebook        1   85.36
Germany 11-Jan-20   Facebook        1   79.77
Germany 12-Jan-20   Facebook    f   1   121.01
Germany 13-Jan-20   Facebook            
Germany 14-Jan-20   Facebook            
Germany 15-Jan-20   Facebook    g   1   

Answer 1

Seems to be your expectation is to get the sum of Leads, Purchases and Revenue. Please use below query,

SELECT
a.Country,    a.Date,    a.Source,    a.Campaign,    sum(a.Leads)    sum(b.purchases),    sum(b.revenue)
FROM
 Table A 
 LEFT JOIN 
 Table B 
ON a.country = b.country and a.date = b.date and a.source = b.source and a.campaign = 
b.campaign;

If this is not what you are expecting, please provide sample data and your expected result. Would be more helpful to provide you the solution

Answer 2

I think you need to use full outer join if you need to get all the data from both tables:

SELECT
ifnull(a.country,b.country) country,
ifnull(a.date,b.date) date,
ifnull(a.source,b.source) source,
ifnull(a.campaign,b.campaign) campaign,
a.leads,
b.purchases,
b.revenue

FROM
Table A 
FULL OUTER JOIN 
Table B 

ON a.country = b.country and a.date = b.date and a.source = b.source and a.campaign = b.campaign

if I misunderstood you question, please provide a sample data

update:

try this:

WITH
  table_a AS (
  SELECT
    'A' Country,
    '2020-01-01' Date,
    'X' Source,
    'L' Campaign,
    100 Leads
  UNION ALL
  SELECT
    'A' Country,
    '2020-01-01' Date,
    'X' Source,
    'L' Campaign,
    200 Leads
  UNION ALL
  SELECT
    'B' Country,
    '2020-01-01' Date,
    'Y' Source,
    'M' Campaign,
    300 Leads
  UNION ALL
  SELECT
    'B' Country,
    '2020-01-01' Date,
    'Y' Source,
    'M' Campaign,
    400 Leads ),
  table_b AS (
  SELECT
    'A' Country,
    '2020-01-01' Date,
    'X' Source,
    'L' Campaign,
    100 Purchases,
    100000 revenue
  UNION ALL
  SELECT
    'A' Country,
    '2020-01-01' Date,
    'X' Source,
    'L' Campaign,
    200 Purchases,
    30000
  UNION ALL
  SELECT
    'B' Country,
    '2020-01-01' Date,
    'Y' Source,
    'M' Campaign,
    400 Purchases,
    40000
  UNION ALL
  SELECT
    'C' Country,
    '2020-01-01' Date,
    'X' Source,
    'L' Campaign,
    200 Purchases,
    30000)
SELECT
  ifnull(a.country,
    b.country) country,
  ifnull(a.date,
    b.date) date,
  ifnull(a.source,
    b.source) source,
  ifnull(a.campaign,
    b.campaign) campaign,
  a.leads,
  b.purchases,
  b.revenue
FROM
  table_a a
FULL OUTER JOIN
  table_b b
ON
  a.country = b.country
  AND a.date = b.date
  AND a.source = b.source
  AND a.campaign = b.campaign

Answer 3

Assuming that your join conditions do not product duplicates, I would suggest using full join with using :

SELECT country, date, source, campaign,
       COALESCE(a.leads, 0) as leads,
       COALESCE(b.purchases, 0) as purchases,
       COALESCE(b.revenue, 0) as revenue
FROM TableA a FULL JOIN
     TableB b
     USING (country, date, source, campaign);

This will keep all rows in both tables. The USING clause makes it easy to avoid NULL values on the key columns used in the JOIN . The COALESCE() is because I'm guessing you really want 0 values for the rows that are in only one table -- but you can remove it if you are happy with NULL .