How to crate physical column in OBIEE physical layer using an expression

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Oracle

BI

I'm new to Oracle BI, I may ask some simple questions for what I could not able to find solution.

I want to join this 2 tables in oracle BI physical layer, how to perform it

Table1
ID Name
A Apple
B Ball
C Cat
D Dog

Table2
Name Price
Apple 10
Ball 15

Please can anyone help me how to join those tables in OBIEE physical layer.

What I have tried:

I tried to join using an expression on join condition
table1.ID= substring(table2.name from 1 for 1)
get below error
[nQSError : 30001] Only columns, designated predicates and operators are allowed.
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I'm trying to create an physical column using an expression Substring but i have no idea how to do.