I'm reading and executing sql queries from file and I need to inspect the result sets to count all the null values across all columns. Because the SQL is read from file, I don't know the column names and thus can't call the columns by name when trying to find the null values.
I think using CTE is the best way to do this, but how can I call the columns when I don't know what the column names are?
WITH query_results AS
(
<sql_read_from_file_here>
)
select count_if(<column_name> is not null) FROM query_results
If you are using Python to read the file of SQL statements, you can do something like this which uses pglast to parse the SQL query to get the columns for you:
import pglast
sql_read_from_file_here = "SELECT 1 foo, 1 bar"
ast = pglast.parse_sql(sql_read_from_file_here)
cols = ast[0]['RawStmt']['stmt']['SelectStmt']['targetList']
sum_stmt = "sum(iff({col} is null,1,0))"
sums = [sum_sql.format(col = col['ResTarget']['name']) for col in cols]
print(f"select {' + '.join(sums)} total_null_count from query_results")
# outputs: select sum(iff(foo is null,1,0)) + sum(iff(bar is null,1,0)) total_null_count from query_results
I am wondering what approach should have been selected to perform action from title. I am using ODBC connection and what I get from first sql query are like 40-50 rows in one column. What I want is to put this output as a values in to search for.
How should i treat this? Like a array or separated variables? I still do not know R well so just need to know where to search for.
Regards
------more explanation below----
I have list of 40-50 numbers of 10 digits each, organized in a column.
I am trying to do this:
list <- c(my_input)
sql_in <- paste0(list, collapse="")
and characters are organized like this after this operations:
'c(1234567890, , 1234567890, 1234567890)'
and almost all looks fine and fit into my query besides additional c character at the beginning and missing apostrophes.I try to use gsub function but did not work in way I want.
You may likely do this in one SQL call using a subquery. Notice in the call below that the result of
SELECT n_gear
FROM Gear
WHERE n_gear IN (3,4)
Is passed to the WHERE clause of the primary query. This is perfectly valid and will allow your query to execute entirely in SQL without having to do any intermediate steps in R.
(I use sqldf for simplicity of illustration, but this should work through just about any ODBC connection)
library(sqldf)
Gear <- data.frame(n_gear = 1:5)
sqldf(
"SELECT mpg, qsec, gear, wt
FROM mtcars
WHERE gear IN (SELECT n_gear
FROM Gear
WHERE n_gear IN (3,4))"
)
Try something like this:
list<-c("try","this") #The output from your first query
sql_in<-paste0(list, collapse="','")
The Output
paste("select * from table where table.var in ",paste("('",sql_in,"')",sep=''))
[1] "select * from table where table.var in ('try','this')"
If yuo have space as first or last element of the string you can use this code:
`list<-c(" first element is a space","try","this","last element is a space ")` #The output from your first query
Find space at first or last character
first_space<-substr(list, start = 1, stop = 1)==" "
last_space<-substr(list, start = nchar(list), stop = nchar(list))==" "
Remove spaces
list[first_space]<-substr(list[first_space], start = 2, stop = nchar(list[first_space]))
list[last_space]<-substr(list[last_space], start = 1, stop = nchar(list[last_space])-1)
sql_in<-paste0(list, collapse="','")
Your output
paste0("select * from table where table.var in ",paste("('",sql_in,"')",sep=''))
"select * from table where table.var in ('first element is a space','try','this','last element is a space')"
I think You are expecting some thing like shown below code,
data <- dbGetQuery(con, "select column from yourfirsttable")
list <- paste(data$column, collapse="','")
result <- dbGetQuery(con, statement = sprintf("select * from yourresulttable where inv in ('%s')",list))
It's not entirely clear exactly what you're wanting to achieve here. For example, one use case just means you can do it all with a join. But I have cases where I don't know the values for the test without doing some computation. Then I do a separate query having created a query string thus:
> id <- 1:5
> paste0("SELECT * FROM table WHERE ID IN (", paste0(id, collapse = ","), ")")
[1] "SELECT * FROM table WHERE ID IN (1,2,3,4,5)"
I'm trying to retrieve some data from a postgresql database using psycogp2, and either exclude a variable number of rows or exclude none.
The code I have so far is:
def db_query(variables):
cursor.execute('SELECT * '
'FROM database.table '
'WHERE id NOT IN (%s)', (variables,))
This does partially work. E.g. If I call:
db_query('593')
It works. The same for any other single value. However, I cannot seem to get it to work when I enter more than one variable, eg:
db_query('593, 595')
I get the error:
psycopg2.DataError: invalid input syntax for integer: "593, 595"
I'm not sure how to enter the query correctly or amend the SQL query. Any help appreciated.
Thanks
Pass a tuple as it is adapted to a record:
query = """
select *
from database.table
where id not in %s
"""
var1 = 593
argument = (var1,)
print(cursor.mogrify(query, (argument,)).decode('utf8'))
#cursor.execute(query, (argument,))
Output:
select *
from database.table
where id not in (593)
When I search for the Dünyas word with a LIKE operator I can see the results but when I search Dünyası word with LIKE operator, it returns no results. Problem is not ı or ü letters I tried with i and u letters as well.
This query:
select * from DbDivx where NameTurkish like '%Dünyas%' =>
returns:
Boksörün Dünyası
Geleceğin Dünyası
Su Dünyası
However:
select * from DbDivx where NameTurkish like '%Dünyası%' =>
returns nothing.
Can you help me please?
http://sqlfiddle.com/#!6/8c359/1
create table test (someName nvarchar(300))
insert into test (someName)
select N'Boksörün Dünyası'
union all select N'Geleceğin Dünyası'
union all select N'Su Dünyası'
select * from test where someName like N'%Dünyası%'
Not having any issues with the above fiddle. Note that when i inserted data without the N in front of it, the like query did not return results.
hopefully this helps!
Not sure how to explain it, unless this is a bug. I'm using VFP OLEDB driver to connect to a DBF database and trying to run the following query:
SELECT id FROM MyDBF WHERE (id > 21800) AND (id < 21820)
I get the following results (copying them on one line to save space):
21810, 21811, 21812, 21813, 21814, 21815, 21816, 21817, 21818, 21819
Now I change the query slightly:
SELECT id FROM MyDBF WHERE (id > 21810) AND (id < 21820)
You expect it to return all of the IDs from previous result except the first one. Booo! The query doesn't return any rows.
Just to make sure I'm not sleepy, I run the following query
SELECT id FROM MyDBF WHERE (id = 21817)
Should return a row, but it doesn't. Not sure what's going on. I have checked the field type and it is OleDbType.Numeric.
So is this me or MS?
I'm posting the workaround I found here to help any future readers. Many thanks to Oleg for his helping hand.
Using INT(id) = 21817 instead of id = 21817 appears to work. Other versions of the SQL statement such as INT(id) BETWEEN x AND y and INT(id) > x AND INT(id) < y also appear to work fine. There's probably some discrepancy between the NUMERIC data type of FoxPro and the way OLEDB driver treats it.