I want to write a test case about null table in dolphindb. But there in the manual ,I can only find how to initialize an int(float/temporal scalar) or a vector....Therefore, how to initialize a null table in dolphindb?
Please use function table to create a null table
colNames =`id`value
colTypes =[INT, DOUBLE]
capacity = 1000
size = 10
t = table(capacity : size, colNames, colTypes)
Related
I need a custom function that takes two parameters, Column1 and Column2, so:
For each Row, return the value of Column1 but only if exists a Value in the Column2 else return null
I have tried this:
let ColumnsFilter = (Tabla,C1,C2)=>
Table.AddColumn(Tabla, "Custom", each if [C2] <> null then [C1] else null)
in
ColumnsFilter
And calling the function:
#"Previous Step" = .....
#"P" = ColumnsFilter(#"Previous Step","Column1","Column2")
in
P
And is not working. clearly I am not using the syntax properly.
In summary I need a table as input and a table as output adding custom columns.
How can I write this?
(Please don't tell me to use the assisted of Power Query, I need to write similar functions manually)
Since you're passing column names as text and individual rows are a record type, you have to use Record.Field to pull the right column (field) from the current row (record).
let
ColumnsFilter = (Tabla as table, C1 as text, C2 as text) as table =>
Table.AddColumn(Tabla, "Custom",
each if Record.Field(_, C2) <> null then Record.Field(_, C1) else null
)
in
ColumnsFilter
I need to add a column that Sums the value column of all columns that have a common id. However, any id = null is not summed, but equal to the value column.
The above example should result in:
TopPaymendId JournalLineNetAmount TopAmount
fcbcd407-ca26-4ea0-839a-c39767d05403 -3623.98 -7061.23
fcbcd407-ca26-4ea0-839a-c39767d05403 -3437.25 -7061.23
ce77faac-1638-40e9-ad62-be1813ce9031 -88.68 -88.68
531d9bde-3f52-47f3-a9cf-6f3566733af2 -152.23 -152.23
8266dfef-dd14-4654-a6d2-091729defde7 229.42 229.42
f8b97a47-15ef-427d-95e0-ce23cc8efb1f -777 -777
null -3.01 -3.01
null -2.94 -2.94
null 3312.5 3312.5
This code should work:
let
Source = Excel.CurrentWorkbook(){[Name="Data"]}[Content],
group = Table.Group(Source, {"TopPaymendId"}, {"TopAmount", each List.Sum([JournalLineNetAmount])}),
join = Table.Join(Source,{"TopPaymendId"},group,{"TopPaymendId"}),
replace = Table.ReplaceValue(join,each [TopAmount],each if [TopPaymendId] = null
then [JournalLineNetAmount] else [TopAmount],Replacer.ReplaceValue,{"TopAmount"})
in
replace
A user can supply answers for up to 5 question, and each question has 3 columns in the database:
st_m1_id
st_m1_fam
st_m1_cip
st_m2_id
st_m2_fam
st_m2_cip
etc
When the form is submitted I get the IDs into an array and then loop over that and then query a different table to look up fam and cip.
aidms = listToArray(form['idms[]']);
for( i=1;i<=arrayLen(aidms);i++ ) {
qryData = invoke(dataCFC,'queryData', { smid = aidms[i]});
temp = invoke(userCFC,'updateUser',{
userid = session.userid,
st_m#i#_id = aidms[i],
st_m#i#_fam = qryData.fam,
etc......
});
};
How do I notate the dynamic query column names in the function so that when they are passed to updateUser the correct columns are referenced?
I'm new to OCaml and i'm trying to understand the concept of mutable record field.
I'd like to create an array of records and that record contains a boolean mutable field. So i did something like:
type t = {i: int; mutable b: bool};;
I want to be able to change the value of the 'b' field of the record, so i put it mutable
let m = Array.make 10 ({i = 5; b = false});;
Here i try to set the b field of the record located at the first index of my array :
(Array.get m 0).b <- true;;
The problem is want i do it, it will set 'b' field of all the records of the array, and this is not what i want.
Does the mutable fields of a same record share the same memory emplacement? How can i do to change the value of the 'b' field of a specific record?
As the documentation states, Array.make creates an array whose elements are all physically equal. That's not a problem if these elements are immutable, but as you saw, you have to take that into account if they are mutable.
What you can do is use Array.init, to create a different object for every cell of your array:
let m = Array.init 10 (fun _ -> {i = 5; b = false});;
Given:
an sqlite database with a table T
the table T contains 10 columns - C0, C1 ... C9.
an sqlite3_stmt pointer corresponding to select C3,C2 from T
OK, so I can fetch the selected column values using the sqlite3_column_XXX family of methods (http://www.sqlite.org/capi3ref.html#sqlite3_column_blob), like this:
sqlite3_stmt *s;
sqlite3_prepare_v2(db, query, sizeof(query), &s, NULL);
while ((result = sqlite3_step(s)) == SQLITE_ROW)
{
const char *v3 = reinterpret_cast<const char *>(sqlite3_column_text(s, 0);
const char *v2 = reinterpret_cast<const char *>(sqlite3_column_text(s, 1);
}
What I need is the real index of the selected columns, i.e. 3 for v3 and 2 for v2.
Motivation: I want to be able to parse the returned string value into the real column type. Indeed, my schema says that c3 is a datetime, which sqlite treats as TEXT. So, sqlite3_column_type(s, 0) returns SQLITE3_TEXT, but the table metadata (available from pragma table_info(T)) retains the string datetime, which is the intended type of the column. Knowing it, I can parse the returned string into the respective unix time since the epoch, for instance.
But how can I map the query column index to the table column index:
query column 0 -> table column 3
query column 1 -> table column 2
Thanks.
You could use the sqlite C function sqlite3_column_decltype to get the declared column data type from the result stmt? It doesn't specifically answer your question (getting the original column's index), but could be an alternative way to achieve what you need?