Power BI is turning 10! Tune in for a special live episode on July 24 with behind-the-scenes stories, product evolution highlights, and a sneak peek at what’s in store for the future.
Save the dateEnhance your career with this limited time 50% discount on Fabric and Power BI exams. Ends August 31st. Request your voucher.
Is there a way to change a list of paired column names and types into a table type? Or maybe way to manipulate types?
let
my_list = { //ideally, the types would be *actual* types, not text
{"UNIQUE_ID", "Number.Type"},
{"NAME", "Text.Type"},
{"START_DATE", "Date.Type"}
},
my_goal = //I want to transform my_list into this:
type table[
UNIQUE_ID = Number.Type,
NAME = Text.Type,
START_DATE = Date.Type
],
//But isn't there a better way than this?
#"My List As Table Type" = Expression.Evaluate(
"type table[#(lf)" & Text.Combine(
List.Transform(
my_list,
each "#(tab)"& _{0} &"="& _{1}
),
",#(lf)"
)&"#(lf)]",
#shared
)
in
#table(
#"My List As Table Type",
{
{1, "Andy", #date(2010,03,25)},
{2, "Sami", #date(2008,06,09)},
{3, "Max", #date(2005,11,03)}
}
)
Solved! Go to Solution.
Thank you!
I'm sorry I wasn't clear on this point, but I specifically needed to get the table type so I could re-use it in later steps. I figured out a method that doesn't use Expression.Evaluate by using List.Accumulate to generate an empty table with typed fields, and wrapping that in Value.Type:
let
my_list = {
{"UNIQUE_ID", Number.Type},
{"NAME", Text.Type},
{"START_DATE", Date.Type}
},
#"My List As Table Type" = Value.Type(
List.Accumulate(
my_list,
#table({},{}), //seed with empty table
(return_table, list_item)=>Table.AddColumn(
return_table,
list_item{0},
each null, //no data, just headers
list_item{1}
)
)
)
in
#table(
#"My List As Table Type",
{
{1, "Andy", #date(2010,03,25)},
{2, "Sami", #date(2008,06,09)},
{3, "Max", #date(2005,11,03)}
}
)
If they are actual types, then Table.TransformColumnTypes does a nice job.
let
my_list =
{
{"UNIQUE_ID", Number.Type},
{"NAME", Text.Type},
{"START_DATE", Date.Type}
},
T1 = #table(
List.Transform(my_list, each _{0}),
{
{1, "Andy", #date(2010,03,25)},
{2, "Sami", #date(2008,06,09)},
{3, "Max", #date(2005,11,03)}
}
)
in
Table.TransformColumnTypes(T1, my_list)
If they are text, then you can transform to types before using them.
let
my_list =
{
{"UNIQUE_ID", "Number.Type"},
{"NAME", "Text.Type"},
{"START_DATE", "Date.Type"}
},
my_types = List.Transform(
my_list, each {_{0}, Expression.Evaluate(_{1}, #shared)}
),
T1 = #table(
List.Transform(my_list, each _{0}),
{
{1, "Andy", #date(2010,03,25)},
{2, "Sami", #date(2008,06,09)},
{3, "Max", #date(2005,11,03)}
}
)
in
Table.TransformColumnTypes(T1, my_types)
Thank you!
I'm sorry I wasn't clear on this point, but I specifically needed to get the table type so I could re-use it in later steps. I figured out a method that doesn't use Expression.Evaluate by using List.Accumulate to generate an empty table with typed fields, and wrapping that in Value.Type:
let
my_list = {
{"UNIQUE_ID", Number.Type},
{"NAME", Text.Type},
{"START_DATE", Date.Type}
},
#"My List As Table Type" = Value.Type(
List.Accumulate(
my_list,
#table({},{}), //seed with empty table
(return_table, list_item)=>Table.AddColumn(
return_table,
list_item{0},
each null, //no data, just headers
list_item{1}
)
)
)
in
#table(
#"My List As Table Type",
{
{1, "Andy", #date(2010,03,25)},
{2, "Sami", #date(2008,06,09)},
{3, "Max", #date(2005,11,03)}
}
)
I still think Table.TransformColumnTypes is useful.
let
my_list =
{
{"UNIQUE_ID", Number.Type},
{"NAME", Text.Type},
{"START_DATE", Date.Type}
},
my_cols = List.Transform(my_list, each _{0}),
my_table_type = Value.Type(
Table.TransformColumnTypes(#table(my_cols,{}), my_list)
),
T1 = #table(
my_table_type,
{
{1, "Andy", #date(2010,03,25)},
{2, "Sami", #date(2008,06,09)},
{3, "Max", #date(2005,11,03)}
}
)
in
T1
Check out the July 2025 Power BI update to learn about new features.
This is your chance to engage directly with the engineering team behind Fabric and Power BI. Share your experiences and shape the future.