大约有 41,000 项符合查询结果（耗时：0.0344秒） [XML]
How do you find the row count for all your tables in Postgres
...th their own tradeoffs.
If you want a true count, you have to execute the SELECT statement like the one you used against each table. This is because PostgreSQL keeps row visibility information in the row itself, not anywhere else, so any accurate count can only be relative to some transaction. Yo...
Real life example, when to use OUTER / CROSS APPLY in SQL
...1) Top N per group queries (can be more efficient for some cardinalities)
SELECT pr.name,
pa.name
FROM sys.procedures pr
OUTER APPLY (SELECT TOP 2 *
FROM sys.parameters pa
WHERE pa.object_id = pr.object_id
ORDER BY pr.n...
Build Android Studio app via command line
... an emulator)
Bonus
I set up an alias in my ~/.bash_profile, to make it a 2char command.
alias bi="gradlew && adb install -r exampleApp.apk"
(Short for Build and Install)
share
|
improve th...
How would you go about parsing Markdown? [closed]
...arkdown extra) I think I would try to use a state machine and parse it one char at a time, linking together some internal structures representing bits of text as I go along then, once all is parsed, generating the output from the objects all stringed together.
Basically, I'd build a mini-DOM-like t...
Row Offset in SQL Server
...
I would avoid using SELECT *. Specify columns you actually want even though it may be all of them.
SQL Server 2005+
SELECT col1, col2
FROM (
SELECT col1, col2, ROW_NUMBER() OVER (ORDER BY ID) AS RowNum
FROM MyTable
) AS MyDerivedTable...
How do I perform HTML decoding/encoding using Python/Django?
...to use the name2codepoint dict to convert each html identity to the actual char it represents.
– Marconius
Jul 9 '12 at 18:43
...
Best way to strip punctuation from a string
...or ch in s if ch not in exclude)
This is faster than s.replace with each char, but won't perform as well as non-pure python approaches such as regexes or string.translate, as you can see from the below timings. For this type of problem, doing it at as low a level as possible pays off.
Timing cod...
Equivalent of LIMIT and OFFSET for SQL Server?
...nation it's better to write a query like this:
;WITH Results_CTE AS
(
SELECT
Col1, Col2, ...,
ROW_NUMBER() OVER (ORDER BY SortCol1, SortCol2, ...) AS RowNum
FROM Table
WHERE <whatever>
)
SELECT *
FROM Results_CTE
WHERE RowNum >= @Offset
AND RowNum < @Offset +...
How to find gaps in sequential numbering in mysql?
...r
Here's version that works on table of any size (not just on 100 rows):
SELECT (t1.id + 1) as gap_starts_at,
(SELECT MIN(t3.id) -1 FROM arrc_vouchers t3 WHERE t3.id > t1.id) as gap_ends_at
FROM arrc_vouchers t1
WHERE NOT EXISTS (SELECT t2.id FROM arrc_vouchers t2 WHERE t2.id = t1.id + ...
When should I use cross apply over inner join?
...APPLY works better on things that have no simple JOIN condition.
This one selects 3 last records from t2 for each record from t1:
SELECT t1.*, t2o.*
FROM t1
CROSS APPLY
(
SELECT TOP 3 *
FROM t2
WHERE t2.t1_id = t1.id
ORDER BY
t2.ran...