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How to count occurrences of a column value efficiently in SQL?
...
This should work:
SELECT age, count(age)
FROM Students
GROUP by age
If you need the id as well you could include the above as a sub query like so:
SELECT S.id, S.age, C.cnt
FROM Students S
INNER JOIN (SELECT age, count(age) a...
Select mySQL based only on month and year
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SELECT * FROM projects WHERE YEAR(Date) = 2011 AND MONTH(Date) = 5
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Postgres: INSERT if does not exist already
...onditional INSERT in PostgreSQL:
INSERT INTO example_table
(id, name)
SELECT 1, 'John'
WHERE
NOT EXISTS (
SELECT id FROM example_table WHERE id = 1
);
CAVEAT This approach is not 100% reliable for concurrent write operations, though. There is a very tiny race condition between...
How to check if a table exists in a given schema
... whether a table (or view) exists, and the current user has access to it?
SELECT EXISTS (
SELECT FROM information_schema.tables
WHERE table_schema = 'schema_name'
AND table_name = 'table_name'
);
The information schema is mainly useful to stay portable across major versions and...
Search an Oracle database for tables with specific column names?
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To find all tables with a particular column:
select owner, table_name from all_tab_columns where column_name = 'ID';
To find tables that have any or all of the 4 columns:
select owner, table_name, column_name
from all_tab_columns
where column_name in ('ID', 'FNAME', ...
How to get a number of random elements from an array?
...- Math.random());
// Get sub-array of first n elements after shuffled
let selected = shuffled.slice(0, n);
DEMO:
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Get selected value/text from Select on change
I need to get the value of the selected option in javascript: does anyone know how to get the selected value or text, please tell how to write a function for it. I have assigned onchange() function to select so what do i do after that?
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Paging with Oracle
... Say, if I pass 10 as a page number, and 120 as number of pages, from the select statement it would give me the 1880th through 1200th, or something like that, my math in my head might be off.
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How to get the first and last date of the current year?
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SELECT
DATEADD(yy, DATEDIFF(yy, 0, GETDATE()), 0) AS StartOfYear,
DATEADD(yy, DATEDIFF(yy, 0, GETDATE()) + 1, -1) AS EndOfYear
The above query gives a datetime value for midnight at the beginning of December 31. This ...
Cannot truncate table because it is being referenced by a FOREIGN KEY constraint?
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IF OBJECT_ID('tempdb..#FKs') IS NOT NULL
DROP TABLE #FKs
-- GET FKs
SELECT ROW_NUMBER() OVER (ORDER BY OBJECT_NAME(parent_object_id), clm1.name) as ID,
OBJECT_NAME(constraint_object_id) as ConstraintName,
OBJECT_NAME(parent_object_id) as TableName,
clm1.name as ColumnName...