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?
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
https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/tools/RelBuilder.java
Here in RelBuilder class documentation for pivot() method provided example is below.
for SQL ::
SELECT * FROM (SELECT mgr, deptno, job, sal FROM emp) PIVOT (SUM(sal) AS ss, COUNT(*) AS c FOR (job, deptno) IN (('CLERK', 10) AS c10, ('MANAGER', 20) AS m20))
RelBuilder.pivot(groupKey, aggCalls, axes, valueMap.build().entrySet())
can be used to create a RelNode object. Here we pass a Map(alias, pivot_column_values) object as "values" parameter.
final Function<RelBuilder, RelNode> f = b -> b.scan("emp")
.pivot(b.groupKey("MGR"), Arrays.asList(b.sum(b.field("SAL")).as("SS"), b.count().as("C")),
b.fields(Arrays.asList("JOB", "DEPTNO")),
ImmutableMap.<String, List<RexNode>>builder()
.put("C10", Arrays.asList(b.literal("CLERK"), b.literal(10)))
.put("M20", Arrays.asList(b.literal("MANAGER"), b.literal(20))).build().entrySet())
.build();
How to pass "values" parameter when we don't have alias for pivot column values.
e.g. how to pass "values" parameter of RelBuilder.pivot() method for below query
SELECT * FROM (SELECT mgr, deptno, job, sal FROM emp) PIVOT (SUM(sal) AS ss, COUNT(*) AS c FOR (job, deptno) IN (('CLERK', 10), ('MANAGER', 20)))
Also is it compulsory to have at least one entry in values Map?
There is a scenario where I receive a string to the bigquery function and need to use it as a column name.
here is the function
CREATE OR REPLACE FUNCTION METADATA.GET_VALUE(column STRING, row_number int64) AS (
(SELECT column from WORK.temp WHERE rownumber = row_number)
);
When I call this function as select METADATA.GET_VALUE("TXCAMP10",149); I get the value as TXCAMP10 so we can say that it is processed as SELECT "TXCAMP10" from WORK.temp WHERE rownumber = 149 but I need it as SELECT TXCAMP10 from WORK.temp WHERE rownumber = 149 which will return some value from temp table lets suppose the value as A
so ultimately I need value A instead of column name i.e. TXCAMP10.
I tried using execute immediate like execute immediate("SELECT" || column || "from WORK.temp WHERE rownumber =" ||row_number) from this stack overflow post to resolve this issue but turns out I can't use it in a function.
How do I achieve required result?
I don't think you can achieve this result with the help of UDF in standard SQL in BigQuery.
But it is possible to do this with stored procedures in BigQuery and EXECUTE IMMEDIATE statement. Consider this code, which simulates the situation you have:
create or replace table d1.temp(
c1 int64,
c2 int64
);
insert into d1.temp values (1, 1), (2, 2);
create or replace procedure d1.GET_VALUE(column STRING, row_number int64, out result int64)
BEGIN
EXECUTE IMMEDIATE 'SELECT ' || column || ' from d1.temp where c2 = ?' into result using row_number;
END;
BEGIN
DECLARE result_c1 INT64;
call d1.GET_VALUE("c1", 1, result_c1);
select result_c1;
END;
After some research and trial-error methods, I used this workaround to solve this issue. It may not be the best solution when you have too many columns but it surely works.
CREATE OR REPLACE FUNCTION METADATA.GET_VALUE(column STRING, row_number int64) AS (
(SELECT case
when column_name = 'a' then a
when column_name = 'b' then b
when column_name = 'c' then c
when column_name = 'd' then d
when column_name = 'e' then e
end from WORK.temp WHERE rownumber = row_number)
);
And this gives the required results.
Point to note: the number of columns you use in the case statement should be of the same datatype else it won't work
i have 2 tables and, i would like to check if table 1 (Type_Sorting) == (CCSClassCode_Type) is matched with table 2 (_Type Sorting) == (_CCS Class Type):
for example, you can see vi got the wrong value in table 1 (CCSClassCode_Type)
and, the right value is XLBas you can see in table 2 (_CCS Class Type) not ULM,
the idea of table 2 to check if people type the right values, Please not that table 2 (_CCS Class Type) have duplicate values
thank you in advance :)
You can calculate this like that:
Table 2 =
Var trt =
SELECTCOLUMNS(Table_2, "XX"
, COMBINEVALUES(",",Table_2[_CCS Class Type],Table_2[_Type Sorting]))
return
SUMMARIZECOLUMNS(Table_1[Column1]
, Table_1[CCSClassCode_Type]
, Table_1[Type_Sorting]
, FILTER(ALL(Table_1[CCSClassCode_Type],Table_1[Type_Sorting]), not( COMBINEVALUES(",",Table_1[CCSClassCode_Type],Table_1[Type_Sorting])
in trt )
))
How can i store all the records of a column in a CDaoRecordSet? I've tried this, but will only return the first record of that column:
rs.Open(dbOpenSnapshot, "SELECT Numar_inmatriculare FROM Masini");
short nFields = rs.GetFieldCount();//returns 1
If i make a "SELECT count(*) AS Numar_inmatriculare FROM Masini" and use rs.GetFieldValue(0) it returns me 13, the correct number of records.
GetFieldCount returns the number of columns in your resultset.
To iterate through the records (=rows), you have to call MoveNext until IsEOF() returns true.
rs.Open(dbOpenSnapshot, "SELECT Numar_inmatriculare FROM Masini");
while(!rs.IsEOF())
{
// do something
rs.MoveNext();
}