使用BASH在基于公共列的文本中跨多行连接列

Question

I have a file like below .

Table1|Column1
Table2|Column1
Table5|Column1
Table3|Column2
Table2|Column2
Table4|Column3
Table2|Column3
Table2|Column4
Table5|Column4
Table2|Column5 

From the below file i am trying to generate a Dynamic SQL JOIn if Tablenames in Column1 have same Attributes

select * from Table1 a inner join Table2 b on a.Column1=b.column1 inner join Table5 c on a.Column1=c.column1 

and

select * from Table3 a inner join Table2 b on a.column2 = b.column2 

..etc till end of file

What is the best way to do it , please advise.

Please note that Same column can appear in more than 2 tables (like upto 20 tables then join will be repeated 19 times)

Answer 1

This is not a complete answer. However, I think you should be able to solve the problem using this answer as a stepping stone.

We use GNU awk for parsing. For better readability we use a script file parse.awk instead of one long command.

# parse.awk
{ a[$2][$1] };
END {
    for (col in a) {
        printf "%s", col;
        for (tab in a[col])
            printf "|%s", tab;
        print ""
    }
}

When we call the script ...

awk -F\| -f parse.awk yourFile

... on your example the output is

Column1|Table5|Table1|Table2
Column2|Table2|Table3
Column3|Table2|Table4
Column4|Table5|Table2
Column5|Table2

From there you should be able to build your SQL commands. You could even adapt parse.awk to generate the SQL commands directly.