** TABLE DDL
============

CREATE TABLE [Table1] (
 [ID] COUNTER,
 [Field1] VARCHAR(255),
 [Field2] LONG DEFAULT 0
);

CREATE UNIQUE INDEX [PrimaryKey] ON [Table1]( [ID] ) WITH PRIMARY;


CREATE TABLE [Table2] (
 [ID] COUNTER,
 [Field1] VARCHAR(255),
 [Field2] LONG DEFAULT 0,
 [Field3] VARCHAR(255)
);

CREATE UNIQUE INDEX [PrimaryKey] ON [Table2]( [ID] ) WITH PRIMARY;

** Now CREATE a NEW query called datqry_SampleNumber
SELECT IIf([Table1].[Field1]="A",[Table1].[Field1] & "-" & [Table1].[Field2],[Table2].[Field1] & "-" & [Table2].[Field2]) AS SampleCode, Table1.Field1
FROM Table1 INNER JOIN Table2 ON Table1.ID = Table2.ID;