How to get a count from all table containing a spe

Question

I have a IBM Content Manager with a DB2 database.

In ICMADMIN, I have a bunch of tables, and some of them contain a specific column (let's call it ID_CLIENT), which is an ID linking to one table (CLIENT).

How can I get the number of rows for each CLIENT from every table containing the ID_CLIENT column?

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I know how to retrieve names of every table containing ID_CLIENT, but not how to join CLIENT on them dynamically.

select tabname from syscat.columns where colname='ID_CLIENT'

(let's call this query A)

So my pseudo query would look like:

select count(*) from CLIENT join (A) on CLIENT.ID_CLIENT = (A).ID_CLIENT

Answer 1

It's possible to accomplish your goal by approaching it as a two-step process:

1. Query the SYSCAT views to generate a separate SQL statement for each potential child table of CLIENT
2. Capture and execute the SQL you generated

WITH ctbls ( tbl ) AS ( SELECT RTRIM( c.tabschema ) || '.' || c.tabname FROM syscat.columns c INNER JOIN syscat.tables t ON t.tabschema = c.tabschema AND t.tabname = c.tabname WHERE c.colname = 'CLIENT_ID' AND c.tabname <> 'CLIENT' -- we don't want to join CLIENT to itself AND t.type = 'T' -- if you want to work with tables only AND c.typename = 'INTEGER' -- if you want only want CLIENT_ID columns of a certain type ) -- Construct a left join between CLIENT and each table returned by the CTE above SELECT 'SELECT ''' || tbl || ''' AS childtablename, par.client_id, COUNT(*) AS childrows ' || 'FROM client par LEFT OUTER JOIN ' || tbl || ' chd ' || 'ON chd.client_id = par.client_id GROUP BY par.client_id;' FROM ctbls ;