大约有 40,000 项符合查询结果（耗时：0.0467秒） [XML]
COUNT(*) vs. COUNT(1) vs. COUNT(pk): which is better? [duplicate]
...ROM boss
LEFT JOIN subordinate on subordinate.boss_id = boss.boss_id
GROUP BY boss.id
But don't use COUNT(*) for LEFT joins, as that will return 1 even if the subordinate table doesn't match anything from parent table
SELECT boss.boss_id, COUNT(*)
FROM boss
LEFT JOIN subordinate on subordinate.bo...
List of all index & index columns in SQL Server DB
... AND ind.is_unique_constraint = 0
AND t.is_ms_shipped = 0
ORDER BY
t.name, ind.name, ind.index_id, ic.is_included_column, ic.key_ordinal;
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Real life example, when to use OUTER / CROSS APPLY in SQL
... WHERE pa.object_id = pr.object_id
ORDER BY pr.name) pa
ORDER BY pr.name,
pa.name
2) Calling a Table Valued Function for each row in the outer query
SELECT *
FROM sys.dm_exec_query_stats AS qs
CROSS APPLY sys.dm_exec_query_plan(qs.plan_handle)
3) Re...
MySQL select one column DISTINCT, with corresponding other columns
...
try this query
SELECT ID, FirstName, LastName FROM table GROUP BY(FirstName)
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What is the id( ) function used for?
...responding C object.
If yes, why doesn't the number increase instantly by the size of the data type (I assume that it would be int)?
Because a list is not an array, and a list element is a reference, not an object.
When do we really use id( ) function?
Hardly ever. id() (or its equivalen...
YouTube API to fetch all videos on a channel
We need a video list by channel name of YouTube (using the API).
14 Answers
14
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How do I select an entire row which has the largest ID in the table?
...want one such row, use @MichaelMior's answer,
SELECT row from table ORDER BY id DESC LIMIT 1
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Efficiently convert rows to columns in sql server
...(ColumnName)
from yourtable
group by ColumnName, id
order by id
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
,1,1,'')
set @query = N'SELECT ' + @cols + N' from
(
selec...
Grouped LIMIT in PostgreSQL: show the first N rows for each group?
I need to take the first N rows for each group, ordered by custom column.
5 Answers
5
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What is the difference between partitioning and bucketing a table in Hive ?
...or department . For a faster query response Hive table can be PARTITIONED BY (country STRING, DEPT STRING). Partitioning tables changes how Hive structures the data storage and Hive will now create subdirectories reflecting the partitioning structure like
.../employees/country=ABC/DEPT=XYZ.
If qu...