I'm using mksqlite to create and access an SQL database from matlab, and I want to get the number of rows in a table. I've tried this:
num = mksqlite('SELECT COUNT(*) FROM myTable');
, but the returned value isn't very helpful. If I put a breakpoint in my script and examine the variable, I find that it's a struct with a single field, called 'COUNT(_)', which seems to actually be an invalid name for a field, so I can't access it:
K>> class(num)
ans =
struct
K>> num
num =
COUNT(_): 0
K>> num.COUNT(_)
??? num.COUNT(_)
|
Error: The input character is not valid in MATLAB statements or expressions.
K>> num.COUNT()
??? Reference to non-existent field 'COUNT'.
K>> num.COUNT
??? Reference to non-existent field 'COUNT'.
Even the MATLAB IDE can't access it. If I try to double click the field in the variable editor, this gets spat out:
??? openvar('num.COUNT(_)', num.COUNT(_));
|
Error: The input character is not valid in MATLAB statements or expressions.
So how can I access this field?
You are correct that the problem is that mksqlite somehow manages to create an invalid field name that can't be read. The simplest solution is to add an AS clause to your SQL so that the field has a sensible name:
>> num = mksqlite('SELECT COUNT(*) AS cnt FROM myTable')
num =
cnt: 0
Then to remove the extra layer of indirection you can do:
>> num = num.cnt;
>> num
num =
0
Related
lv_objectkey2 = ls_mseg-matnr.
"Transport Category
CALL FUNCTION 'BAPI_OBJCL_GETDETAIL'
EXPORTING
objectkey = lv_objectkey2
objecttable = 'MARA'
classnum = 'Z_MATERIAL_CLASS'
classtype = '001'
TABLES
allocvaluesnum = lt_allocvaluesnum2
allocvalueschar = lt_allocvalueschar2
allocvaluescurr = lt_allocvaluescurr2
return = lt_return2.
READ TABLE lt_allocvaluesnum2 INTO ls_valnum2 WITH KEY charact= 'Z_ADR_QUANTITY'.
IF sy-subrc = 0.
lv_adr_quan = ls_valnum2-value_from + lv_adr_quan.
WRITE: lv_adr_quan TO ls_item-ADR_QUAN EXPONENT 0 DECIMALS 2.
* CONDENSE ls_item-ADR_QUAN.
ENDIF.
Here is my problem : The program gives me that problem : "ADR_QUAN" must be a character-type field (data type C, N, D or T).
I need your opinions to fix the issue or solutions.
CONDENSE Statement works only for the character-like variables. Here, ls_item-ADR_QUAN field is of type Float, That's why you're getting that error.
You can go through the attached documentation link for CONDENSE statement.
CONDENSE Documentation
Even if you want to perform CONDENSE then first, you've to assign ls_item-ADR_QUAN to a character-like variable.
I have a procedure with the parameter IT_ATINN:
IMPORTING
REFERENCE(IT_ATINN) TYPE STRING_TABLE
IT_ATINN contains a list of characteristics.
I have the following code:
LOOP AT values_tab INTO DATA(value).
SELECT ( #value-INSTANCE ) AS CUOBJ
FROM IBSYMBOL
WHERE SYMBOL_ID = #value-SYMBOL_ID
AND ATINN ??? "<======== HERE ???
APPENDING TABLE #DATA(ibsymbol_tab).
ENDLOOP.
How can I check if ATINN (in the WHERE clause) is equal to any entry in IT_ATINN?
To achieve what you want (and I assume you want dynamic SELECT fields) you cannot use inline declarations here, both in LOOP and in SELECT:
The structure of the results set must be statically identifiable. The SELECT list and the FROM clause must be specified statically and host variables in the SELECT list must not be generic.
So either you use inline or use dynamics, not both.
Here is the snippet that illustrates Sandra good suggestion:
TYPES: BEGIN OF ty_value_tab,
instance TYPE char18,
symbol_id TYPE id,
END OF ty_value_tab.
DATA: it_atinn TYPE string_table.
DATA: rt_atinn TYPE RANGE OF atinn,
value TYPE ty_value_tab,
values_tab TYPE RANGE OF ty_value_tab,
ibsymbol_tab TYPE TABLE OF ibsymbol.
rt_atinn = VALUE #( FOR value_atinn IN it_atinn ( sign = 'I' option = 'EQ' low = value_atinn ) ).
APPEND VALUE ty_value_tab( instance = 'ATWRT' ) TO values_tab.
LOOP AT values_tab INTO value.
SELECT (value-instance)
FROM ibsymbol
WHERE symbol_id = #value-symbol_id
AND atinn IN #rt_atinn
APPENDING CORRESPONDING FIELDS OF TABLE #ibsymbol_tab.
ENDLOOP.
Overall, it makes no sense select ibsymbol in loop, 'cause it has only 8 fields, so you can easily collect all necessary fields from values_tab and pass them as dynamic fieldstring.
If you wanna use alias CUOBJ for your dynamic field you should add it like this:
LOOP AT values_tab INTO value.
DATA(aliased_value) = value-instance && ` AS cuobj `.
SELECT (aliased_value)
...
Remember, that your alias should exists among ibsymbol fields, otherwise in case of static ibsymbol_tab declaration this statement will throw a short dump.
When using primitive types such as Integer, I can without any problems do a query like this:
with connection.cursor() as cursor:
cursor.execute(sql='''SELECT count(*) FROM account
WHERE %(pk)s ISNULL OR id %(pk)s''', params={'pk': 1})
Which would either return row with id = 1 or it would return all rows if pk parameter was equal to None.
However, when trying to use similar approach to pass a list/tuple of IDs, I always produce a SQL syntax error when passing empty/None tuple, e.g. trying:
with connection.cursor() as cursor:
cursor.execute(sql='''SELECT count(*) FROM account
WHERE %(ids)s ISNULL OR id IN %(ids)s''', params={'ids': (1,2,3)})
works, but passing () produces SQL syntax error:
psycopg2.ProgrammingError: syntax error at or near ")"
LINE 1: SELECT count(*) FROM account WHERE () ISNULL OR id IN ()
Or if I pass None I get:
django.db.utils.ProgrammingError: syntax error at or near "NULL"
LINE 1: ...LECT count(*) FROM account WHERE NULL ISNULL OR id IN NULL
I tried putting the argument in SQL in () - (%(ids)s) - but that always breaks one or the other condition. I also tried playing around with pg_typeof or casting the argument, but with no results.
Notes:
the actual SQL is much more complex, this one here is a simplification for illustrative purposes
as a last resort - I could alter the SQL in Python based on the argument, but I really wanted to avoid that.)
At first I had an idea of using just 1 argument, but replacing it with a dummy value [-1] and then using it like
cursor.execute(sql='''SELECT ... WHERE -1 = any(%(ids)s) OR id = ANY(%(ids)s)''', params={'ids': ids if ids else [-1]})
but this did a Full table scan for non empty lists, which was unfortunate, so a no go.
Then I thought I could do a little preprocessing in python and send 2 arguments instead of just the single list- the actual list and an empty list boolean indicator. That is
cursor.execute(sql='''SELECT ... WHERE %(empty_ids)s = TRUE OR id = ANY(%(ids)s)''', params={'empty_ids': not ids, 'ids': ids})
Not the most elegant solution, but it performs quite well (Index scan for non empty list, Full table scan for empty list - but that returns the whole table anyway, so it's ok)
And finally I came up with the simplest solution and quite elegant:
cursor.execute(sql='''SELECT ... WHERE '{}' = %(ids)s OR id = ANY(%(ids)s)''', params={'ids': ids})
This one also performs Index scan for non empty lists, so it's quite fast.
From the psycopg2 docs:
Note You can use a Python list as the argument of the IN operator using the PostgreSQL ANY operator.
ids = [10, 20, 30]
cur.execute("SELECT * FROM data WHERE id = ANY(%s);", (ids,))
Furthermore ANY can also work with empty lists, whereas IN () is a SQL syntax error.
I created two string variables (tot and tot_value) and assigned a value (tot = MyVal) for testing. Then I created an Execute SQL Task which takes (tot) as parameter and the value returned is saved in tot_value.
In the General Tab, i set:
ResultSet to Single row. SQL Source Type to Direct input Query is listed below.
In Parameter Mapping I selected my tot variable with Input DirectionSQL_VARCHAR Data Type 1 as Parameter Name (Since i am using ODBC)Size set to default -1.
In Result SetResult Name to 1Variable Name to tot_value.
If in the query I hard code 'MyVal' i get the correct result, however when I use ? to use my variable as a parameter, I always get a 0 returned.
Note that my tot variable is set to MyVal
Any clue of what I might be missing? Thanks in advance
select TOP 1 CAST('' + ISNULL((SELECT distinct type_of_transfer_code
FROM SYSTEM.history_program_transfer
WHERE type_of_transfer_value = ?),'') AS VARCHAR(100)) as type_of_transfer_code
FROM SYSTEM.table_facility_defaults
I am trying to read a table having five rows and columns. I have used sql.eachRow function to read eachRow and assign the value to a String. I am getting an error "Groovy:[Static type checking] - No such property: MachineName for class: java.lang.Object"
My code:
sql.eachRow('select * from [MACHINES] WHERE UpdateTime > :lastTimeRead, [lastTimeRead: Long.parseLong(lastTimeRead)])
{ row ->
def read = row.MachineName
}
but MachineName is my column name. How can i overcome this error.
Using dynamic Properties with static type checking is not possible*.
However, eachRow will pass a GroovyResultSet as first parameter to the Closure. This means that row has the type GroovyResultSet and so you can access the value using getAt
row.getAt('MachineName')
should work. In groovy you can also use the []-operator:
row['MachineName']
which is equivalent to the first solution.
*) without a type checking extension.
If you Know the Column name you can just use the Below.
"$row.MachineName"
But if you don't Know column name or having some issue, still it can be accessed using an array of Select.
sql.eachRow('select * from [MACHINES] WHERE UpdateTime > :lastTimeRead, [lastTimeRead: Long.parseLong(lastTimeRead)])
{ row->
log.info "First value = ${row[0]}, next value = ${row[1]}"
}