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    <p>Why combine the 3 tables into one? Would be really bad db design. But here's a way to do it:</p> <p>The one table will have a column for each of the 3 tables' columns you want in the final table. I am making the assumption that <code>TableX_Hash</code> is the same type, so that remains as one unique column:</p> <pre><code>Table_All_in_One ( Table1_PK1, Table1_PK2, Table1_PK3, # space just for clarity of grouping Table2_PK1, Table2_PK2, Table3_PK1, Table3_PK2, Table3_PK3, Table3_PK4, Table3_PK5, TableX_Hash # Assuming all the _Hash'es are the same type+length, # otherwise, add Table1_Hash, Table2_Hash, Table3_Hash # This can be your new primary key ) </code></pre> <p>The Primary Keys (<code>PKx</code>) are required to be non-<code>NULL</code> only in their own tables. For this table, they have to allow nulls. <strong>The idea is that each row of this new table will only hold the data for one of the tables. The other columns will be empty for that row.</strong> If you want to associate the row of one table with another, you can add that to the same row or add <code>FK_Table1_Hash</code>, <code>FK_Table2_Hash</code> and <code>FK_Table3_Hash</code> columns which will refer to the <code>TableX_Hash</code> value of a record.</p> <p>PS: I wonder if what you are really looking for is a <code>View</code> and not this really bad all-in-one table.</p> <hr> <p>Edit: Combining them into one "without knowing how many primary keys a table can have." as per your comment:</p> <p>Store all the _PKs concatenated into one column:</p> <pre><code>Table_All_in_One ( New_PK, TableX_Hash, Table1_PKx, # Concatenated PKs of Table1 Table2_PKx, # Concatenated PKs of Table2, etc. ..., # OR just one TableX_PKs, # concatenate all the PK's into one VARCHAR field # Add a pipe `|` between them optionally. Table_Num # If using just one, then you'll need to store the table number </code></pre> <p>) You will not be able to conveniently pick records based on <em>part</em> of their composite primary key. It will always have to be <code>TableX_PKs = CONCAT_WS('|', Table1_PK1, Table1_PK2, ...)</code>. So your only dependency is the number of PKs in the original column.</p>
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    1. POA single table that represents multiple tables
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    1. COThanks for your post, but this not what i am looking for. All of 3 tables are really independent in term of all the fields they have. Lets say if i want to add data of Table10 which has 10 columns of 10 primary keys into Table_All_in_One, this would fail.
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    2. COThis would work fine even then. You just need to make sure that the `Table_All_in_One` has all the columns of every other table. When you add the data of the 10 columns of table 10 to All_in_One (`Table10_PK1, _PK2..., PK10`) the remaining columns of All_in_One (`Table2_PK1, Table3_PK5`, etc.) would be empty/`NULL`.
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    3. COHmm... I am still looking for a dynamic way to do it without knowing how many primary keys a table can have.
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