Table Contains syntax explanation

[Dicken]

  
An example of Table.Contains has the following  

Table.Contains( 
    Table.FromRecords( {
        [CustomerID = 1, Name = "Bob", Phone = "123-4567"],
        [CustomerID = 2, Name = "Jim", Phone = "987-6543"],
        [CustomerID = 3, Name = "Paul", Phone = "543-7890"],
        [CustomerID = 4, Name = "Ringo", Phone = "232-1550"]
    } ),
    [CustomerID = 4, Name = "Bob"],
    "Name"
 )

But you could just re write as ; are there reasons why or is it just a cose the you have columns stored as reocrds and just want to specify a partiuclar one ? 

= Table.Contains(
Table.FromRecords( {
[CustomerID = 1, Name = "Bob", Phone = "123-4567"],
[CustomerID = 2, Name = "Jim", Phone = "987-6543"],
[CustomerID = 3, Name = "Paul", Phone = "543-7890"],
[CustomerID = 4, Name = "Ringo", Phone = "232-1550"]
} ),
[Name = "Bob"]
)  

 I cant find any information as t why include to columns and then specify  a true false from only one , why not just write ; 

Are there reasons I'm overlooking as to why 

Richard

[watkinnc · Accepted solution]

It's so that you can match on the name value in a specific record, whatever that name value might be--it might not always be "Bob". So if you have a list of records, which is what a table is, and you want to check if another table contains the name that is in the current row/record. This is especially useful when you have a column of nested tables, so if you have a "Name" column in your table, and you have a column of nested tables that also have a "Name" column, and you want to keep rows where "Name" matches the "Name" in the nested table. So 

each Table.Contains([NestedTableColumnName, _, "Name")

--Nate

[PwerQueryKees · Accepted solution]

Good question. As the official documentation tells us the third parameter should be a comparere function, not a string....

I do see why you would want to name a column (is a list of columns also supported??) to limit the comparison to if the record for the first parameter comes from another table, because it saves a Table.SelectColumns(). At least a convenience and possible a perfromance advantage.

[Dicken]

Thanks, 

RD

[watkinnc · Accepted solution]

It's so that you can match on the name value in a specific record, whatever that name value might be--it might not always be "Bob". So if you have a list of records, which is what a table is, and you want to check if another table contains the name that is in the current row/record. This is especially useful when you have a column of nested tables, so if you have a "Name" column in your table, and you have a column of nested tables that also have a "Name" column, and you want to keep rows where "Name" matches the "Name" in the nested table. So 

each Table.Contains([NestedTableColumnName, _, "Name")

--Nate

[Dicken]

That's prettey much what I thought as I couldn't think of another use, but thought there might be something  overlooked.

[tharunkumarRTK]

@Dicken 

I guess this article answers your question: 

https://powerquery.how/table-contains/

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[Dicken]

Not really as that is what provoked the qustion; differece; 

 [Name = "Bob"]

and ; 

 [CustomerID = 4, Name = "Bob"],
    "Name"