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Update Column

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stahorse
Yak Posting Veteran

86 Posts

Posted - 2014-02-11 : 02:53:10

I have two tables;

CUSTOMER (customer_id NUMBER, customer_name VARCHAR2(100), recently_purchased VARCHAR2(1))

and

CUST_PRODUCTS (product_id NUMBER, customer_id NUMBER, date_purchased DATE);

I need to update CUSTOMER, to set recently_purchased = 'Y' if product purchased products are in the last 12 months.

I know that two tables has to be joined and I can use CUST_PRODUCTS where DATEDIFF(month,date_purchased, GETDATE()) <= 12, but I can't get my query right. please help.

visakh16
Very Important crosS Applying yaK Herder

52326 Posts

Posted - 2014-02-11 : 03:00:59

[code]
UPDATE c
SET recently_purchased = 'Y'
FROM Customer c
WHERE EXISTS (SELECT 1
FROM CUST_PRODUCTS
WHERE customer_id = c.customer_id
AND date_purchased >= DATEADD(mm,DATEDIFF(mm,0,GETDATE())-12,0)
)
[/code]

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Kristen
Test

22859 Posts

Posted - 2014-02-11 : 03:27:34

quote:
Originally posted by stahorse

where DATEDIFF(month,date_purchased, GETDATE()) <= 12

Visakh's code looks fine. You might(??) need to alias the CUST_PRODUCTS table (I'm not sure without trying it). Code below.

Personally I suggest you stick with "month" as the first parameter of DATEDIFF. The short abbreviations are probably fine for folk that use them everyday - but then along comes someone [less skilled] doing code maintenance and they may not spot that an abbreviation is wrong. Is "mm" Month, Minute, Millisecond, Microsecond ? "mm" is the most obvious of those, the others less so ... so here we always use the full parameter name.


UPDATE c
SET recently_purchased = 'Y'
FROM Customer c
WHERE EXISTS (SELECT 1
FROM CUST_PRODUCTS AS P
WHERE P.customer_id = c.customer_id 
AND date_purchased >= DATEADD(month,DATEDIFF(month,0,GETDATE())-12,0)
)

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