How to obtain row counts for all tables in Netezza

You can't have more than one primary key on a table - I assume you mean foreign keys. There is no best way to do this, because it depends upon your workload. In some indexes one column may come first, while another may have a completely different selection of columns, let alone order.

In the end it doesn't really matter, because Netezza doesn't have indexes in the first place, so I'm not sure what you're getting at.

That is a composite primary key made up of all those columns. Together they are "unique" (Netezza doesn't enforce this) and uniquely identify the row. This is typical in a dimensional design. The FKs of a large number of dimensions uniquely identify a fact - usually a date/time for the snapshot, and something like a stock ticker or customer or whatever.

I found this guide which is for Netezza version 5, so that should be close. Documentation for that system is rather difficult to find, or at least it doesn't readily show up on Google. For SQL Server 2008, the MSDN page is here.

ABSTIME --> ??
BIGINT --> bigint
BOOLEAN --> bit
BYTEA --> ?? tinyint?
BYTEINT --> smallint (tinyint is positive values only)
CHAR --> char(1)
CHARACTER VARYING(1..8000) --> varchar(1..8000)
CHARACTER VARYING(>8000) --> varchar(MAX)
CHARACTER(1..8000) --> char(1..8000)
DATE --> date
DOUBLE PRECISION --> double precision or float(53)
INT2VECTOR --> ??
INTEGER --> int
INTERVAL --> No equivalent
NAME --> ?? sysname?
NATIONAL CHARACTER VARYING(1..4000) --> nvarchar(1..4000)
NATIONAL CHARACTER VARYING(>4000) --> nvarchar(MAX)
NUMERIC(p,s) --> numeric(p,s)
OID --> ??
OIDVECTOR --> ??
REAL --> real
REGPROC --> ??
SMALLINT --> smallint
TEXT --> ?? Probably either varchar(MAX) or nvarchar(MAX)
TIME --> time(6)
TIME WITH TIME ZONE --> datetimeoffset(6)
TIMESTAMP --> datetime2(6)