I need to read the column value of the following query
SELECT strtime('%Y-%m', created_at) as field FROM table GROUP BY field
the type of column field is 3 (I assume it is blog), but I need string
How should I?
Updated
const char* sql =
"SELECT CAST(strftime('%Y', created_at) as INTEGER) as year FROM table GROUP BY year
if (SQLITE_OK == sqlite3_prepare_v2([AppDelegate db], sql, -1, &queryhandle, NULL)){
while(SQLITE_ROW == sqlite3_step(queryhandle)){
NSSTring* year = [NSString stringWithFormat:#"%d",sqlite3_column_int(queryhandle, 0)];
this code gives me 3460 as year
(have checked cast as integer, and cast as varchar and sqlite3_column_text function)
As long as created_at has a time string format as specified in the sqlite docs, it doesn't matter what storage type is used in a particular tuple (although you can find out using the typeof) function. The result of the strftime function (you aliased it as field) is either text or null.
CREATE TABLE t (x BLOB);
INSERT INTO t VALUES ("2010-03-29\x0"), ("2010-03-28");
SELECT strftime("%Y-%m", x), typeof(strftime("%Y-%m", x)), typeof(x) FROM t;
|null|text
2010-03|text|text
Related
select *
from nsclc_thought_spot
where patientid = 11000001
and service_date in ('2019-07-08', '2019-07-10')
order by patientid, service_date
is returning the results properly
But this is not working as expected:
select *
from nsclc_thought_spot
where patientid = 11000001
and service_date in (2019-07-08, 2019-07-10)
order by patientid, service_date
This query is not returning results.
If I have defined service_date column as date, then why do I have to pass the values in quotes inside IN operator in redshift?
Because 2019-07-08 means the integer 2019 minus the integer 7 minus the integer 8 which equals the integer 2004. Without quotes in SQL numbers are seen as numeric values. To be interpreted as something else you need to quote them (which is a text value) and then they need to be cast to the data type needed. In this case '2019-07-08' is a text value but Redshift will implicitly cast this to a date to make the comparison to the column data "service_date".
If you want to do this explicitly you can add the casting to the values - ... service_date IN ('2019-07-08'::date,'2019-07-10'::date) ... - which might make things clearer for you.
In MongoDB you can retrieve the date from an ObjectId using the getTimestamp() function. How can I retrieve the date from a MongoDB ObjectId using Postgresql (e.g., in the case where such an ObjectId is stored in a Postgres database)?
Example input:
507c7f79bcf86cd7994f6c0e
Wanted output:
2012-10-15T21:26:17Z
In Mongodb documentation the Objectid is formed with a timestamp as the first 4 bytes, but this is represented in hexidecimal. Assuming that hexidecimal value is stored as a string in PostgreSQL, then the following query will extract just the first 8 characters of that objectid, convert that to an integer (which is seconds from 1970-01-01) then convert that integer to a timestamp. For example:
SELECT TO_TIMESTAMP(int_val) ts_val
FROM (
SELECT ('x' || lpad(left(objectid,8), 8, '0'))::bit(32)::int AS int_val
FROM (
VALUES ('507c7f79bcf86cd7994f6c0e')
) AS t1(objectid)
) AS t2
;
Converting a hexadecimal string to integer is discussed here:
Convert hex in text representation to decimal number
The first answer is quite excellent. This one expands the answer by making a reusable function out of it.
create function extractMongoTimestamp(text) RETURNS TIMESTAMP WITH TIME ZONE
as
'SELECT TO_TIMESTAMP(int_val) ts_val
FROM (
SELECT (''x'' || lpad(left(objectid,8), 8, ''0''))::bit(32)::int AS int_val
FROM (
VALUES ($1)
) AS t1(objectid)
) AS t2'
language sql
immutable
RETURNS null on null input;
Use it in your query:
select extractMongoTimestamp('507c7f79bcf86cd7994f6c0e');
I need to include EXTRACT() function within WHERE clause as follow:
SELECT * FROM my_table WHERE EXTRACT(YEAR FROM date) = '2014';
I get a message like this:
pg_catalog.date_part(unknown, text) doesn't exist**
SQL State 42883
Here is my_table content (gid INTEGER, date DATE):
gid | date
-------+-------------
1 | 2014-12-12
2 | 2014-12-08
3 | 2013-17-15
I have to do it this way because the query is sent from a form on a website that includes a 'Year' field where users enter the year on a 4-digits basis.
The problem is that your column is of data type text, while EXTRACT() only works for date / time types.
You should convert your column to the appropriate data type.
ALTER TABLE my_table ALTER COLUMN date TYPE date;
That's smaller (4 bytes instead of 11 for the text), faster and cleaner (disallows illegal dates and most typos).
If you have non-standard format add a USING clause with a conversion expression. Example:
Alter character field to date
Also, for your queries to be fast with a plain index on date you should rather use sargable predicates. Like:
SELECT * FROM my_table
WHERE date >= '2014-01-01'
AND date < '2015-01-01';
Or, to go with your 4-digit input for the year:
SELECT * FROM my_table
WHERE date >= to_date('2014', 'YYYY')
AND date < to_date('2015', 'YYYY');
You could also be more explicit:
to_date('2014' || '0101', 'YYYYMMNDD')
Both produce the same date '2014-01-01'.
Aside: date is a reserved word in standard SQL and a basic type name in Postgres. Don't use it as identifier.
This happens because the column has a text or varchar type, as opposed to date or timestamp. This is easily reproducible:
SELECT 1 WHERE extract(year from '2014-01-01'::text)='2014';
yields this error:
ERROR: function pg_catalog.date_part(unknown, text) does not exist
LINE 1: SELECT 1 WHERE extract(year from '2014-01-01'::text)='2014';
^ HINT: No function matches the given name and argument types. You might need to add explicit type casts.
extract or is underlying function date_part does not exist for text-like datatypes, but they're not needed anyway. Extracting the year from this date format is equivalent to getting the 4 first characters, so your query would be:
SELECT * FROM my_table WHERE left(date,4)='2014';
My query looks like this:
SELECT mthreport.*
FROM crosstab
('SELECT
to_char(ipstimestamp, ''mon DD HH24h'') As row_name,
varid::text || log.varid || ''_'' || ips.objectname::text As bucket,
COUNT(*)::integer As bucketvalue
FROM loggingdb_ips_boolean As log
INNER JOIN IpsObjects As ips
ON log.Varid=ips.ObjectId
WHERE ((log.varid = 37551)
OR (log.varid = 27087)
OR (log.varid = 50876)
OR (log.varid = 45096)
OR (log.varid = 54708)
OR (log.varid = 47475)
OR (log.varid = 54606)
OR (log.varid = 25528)
OR (log.varid = 54729))
GROUP BY to_char(ipstimestamp, ''yyyy MM DD HH24h''), row_name, objectid, bucket
ORDER BY to_char(ipstimestamp, ''yyyy MM DD HH24h''), row_name, objectid, bucket' )
As mthreport(item_name text, varid_37551 integer,
varid_27087 integer ,
varid_50876 integer ,
varid_45096 integer ,
varid_54708 integer ,
varid_47475 integer ,
varid_54606 integer ,
varid_25528 integer ,
varid_54729 integer ,
varid_29469 integer)
the query can be tested against a test table with this connection string:
"host=bellariastrasse.com port=5432 dbname=IpsLogging user=guest password=guest"
The query is syntactically correct and runs fine. My problem is that it the COUNT(*) values are always filling the leftmost column. however, in many instances the left columns should have a zero, or a NULL, and only the 2nd (or n-th) column should be filled. My brain is melting and I cannot figure out what is wrong!
The solution for your problem is to use the crosstab() variant with two parameters.
The second parameter (another query string) produces the list of output columns, so that NULL values in the data query (the first parameter) are assigned correctly.
Check the manual for the tablefunc extension, and in particular crosstab(text, text):
The main limitation of the single-parameter form of crosstab is that
it treats all values in a group alike, inserting each value into the
first available column. If you want the value columns to correspond to
specific categories of data, and some groups might not have data for
some of the categories, that doesn't work well. The two-parameter form
of crosstab handles this case by providing an explicit list of the
categories corresponding to the output columns.
Emphasis mine. I posted a couple of related answers recently here or here or here.
I have SQL query statement which used to display the contents in the table. The SQL statement consist of a where clause which is to be appended with numeric value as 1 ,2 3 etc depends upon the previously selected content. I am having the numeric value as int and I want it to append to SQL statement which is const char. How can I append both the values?
My query is:
select * from Book where id=1;
I have the id value is integer
You simply bind the parameter. E.g.:
sqlite3 *db;
... // open database
sqlite3_stmt *pStmt;
sqlite3_prepare_v2(
db,
"select * from book where id = ?",
-1,
&pStmt,
NULL
);
sqlite3_bind_int(pStmt, 1, bookId);
See the SQLite documentation on compiling and binding prepared statements. You can reuse the same statement more than once. sqlite3_clear_bindings lets you reset the values.
Is this what you're looking for?
NSString* result = [NSString stringWithFormat:#"SELECT * FROM Book WHERE id=%d", myInt];
to compose your SQL string?