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how to exclude null values in array_agg like in string_agg using postgres?
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SQL Fiddle
select
id,
(select array_agg(a) from unnest(canonical_users) a where a is not null) canonical_users,
(select array_agg(a) from unnest(non_canonical_users) a where a is not null) non_canonical_users
from (
SELE...
C++ valarray vs. vector
...ample. (By the way, if mean is really int, not double, you may need static_cast<double>(mean).)
– musiphil
Mar 27 '13 at 23:12
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Returning a C string from a function
...you about that return line converting a char * to char without an explicit cast.
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Is there a way to check if a file is in use?
...which is more typing. If you have a explicit interface you'd also have to cast. Finally you want to dispose ASAP, and the finally logic may have UI or any other long running actions that have little to do with calling IDispose. </rant>
– Spence
Nov 27 '...
Get record counts for all tables in MySQL database
...get the count of rows in all tables in a MySQL database without running a SELECT count() on each table?
19 Answers
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Create a temporary table in a SELECT statement without a separate CREATE TABLE
Is it possible to create a temporary (session only) table from a select statement without using a create table statement and specifying each column type? I know derived tables are capable of this, but those are super-temporary (statement-only) and I want to re-use.
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selecting unique values from a column
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Use the DISTINCT operator in MySQL:
SELECT DISTINCT(Date) AS Date FROM buy ORDER BY Date DESC;
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MySQL Insert Where query
...INSERT INTO Users(weight, desiredWeight)
VALUES (160,145)
INSERT using a SELECT statement
INSERT INTO Users(weight, desiredWeight)
SELECT weight, desiredWeight
FROM AnotherTable
WHERE id = 1
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Passing an array to a query using a WHERE clause
...y external input is sanitized.
$ids = join("','",$galleries);
$sql = "SELECT * FROM galleries WHERE id IN ('$ids')";
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SELECT * FROM X WHERE id IN (…) with Dapper ORM
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Dapper supports this directly. For example...
string sql = "SELECT * FROM SomeTable WHERE id IN @ids"
var results = conn.Query(sql, new { ids = new[] { 1, 2, 3, 4, 5 }});
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