How do I select the max value from multiple tables in one column

I would like to get开发者_如何学运维 the last date of records modified. Here is a sample simple SELECT:

SELECT
 t01.name,
 t01.last_upd date1,
 t02.last_upd date2,
 t03.last_upd date3,
 'maxof123' maxdate
FROM
  s_org_ext   t01,  
  s_org_ext_x   t02,   
  s_addr_org   t03   
WHERE
  t02.par_row_id(+)= t01.row_id and
  t03.row_id(+)= t01.pr_addr_id and
  t01.int_org_flg = 'n';

How can I get column maxdate to display the max of the three dates?

Note: no UNION or sub/nested SELECT statements ;)

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Greatest (t01.last_upd, t02.last_upd date2, t03.last_upd ) as maxdate

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use a CASE statement in your SELECT clause to do something like:

CASE WHEN date1 > date2 AND date1 > date3 THEN date1 WHEN date2 > date3 THEN date2 ELSE date3 END AS maxdate

It will break out of the logic as soon as the first condition is met.

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Use the GREATEST function, also used explicit joins rather than implicit joins.

SELECT t01.name, t01.last_upd date1, t02.last_upd date2, t03.last_upd date3,
GREATEST(t01.last_upd, t02.last_upd, t03.last_upd) AS maxdate 
FROM s_org_ext t01
LEFT OUTER JOIN s_org_ext_x t02 ON t01.row_id = t02.par_row_i
LEFT OUTER JOIN s_addr_org t03 ON t01.pr_addr_id = t03.row_id
WHERE t01.int_org_flg = 'n';