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Fastest way to count exact number of rows in a very large table?
I have come across articles that state that SELECT COUNT(*) FROM TABLE_NAME will be slow when the table has lots of rows and lots of columns.
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Dynamic Sorting within SQL Stored Procedures
...eing duplicated twice in the order by, and is a little more readable IMO:
SELECT
s.*
FROM
(SELECT
CASE @SortCol1
WHEN 'Foo' THEN t.Foo
WHEN 'Bar' THEN t.Bar
ELSE null
END as SortCol1,
CASE @SortCol2
WHEN 'Foo' THEN t.Foo
WHEN 'Bar' THEN t.Bar
ELSE...
Split string, convert ToList() in one line
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var numbers = sNumbers.Split(',').Select(Int32.Parse).ToList();
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XPath: How to select elements based on their value?
...st thing is when using [], there are only two types of data:
[number] to select a node from node-set
[bool] to filter a node-set from node-set
In this case, the value is evaluated to boolean by function boolean(), and there is a rule:
Filters are always evaluated with respect to a context.
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How to select label for=“XYZ” in CSS?
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The selector would be label[for=email], so in CSS:
label[for=email]
{
/* ...definitions here... */
}
...or in JavaScript using the DOM:
var element = document.querySelector("label[for=email]");
...or in JavaScript using...
Get table name by constraint name [duplicate]
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SELECT owner, table_name
FROM dba_constraints
WHERE constraint_name = <<your constraint name>>
will give you the name of the table. If you don't have access to the DBA_CONSTRAINTS view, ALL_CONSTRAINTS or US...
Freezing Row 1 and Column A at the same time
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Select cell B2 and click "Freeze Panes" this will freeze Row 1 and Column A.
For future reference, selecting Freeze Panes in Excel will freeze the rows above your selected cell and the columns to the left of your selected ce...
Use a list of values to select rows from a pandas dataframe [duplicate]
...andas.pydata.org/pandas-docs/stable/… for more details. A sort after the selection is needed.
– Wouter Overmeire
Aug 18 '14 at 15:16
1
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Select Pandas rows based on list index
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For large datasets, it is memory efficient to read only selected rows via the skiprows parameter.
Example
pred = lambda x: x not in [1, 3]
pd.read_csv("data.csv", skiprows=pred, index_col=0, names=...)
This will now return a DataFrame from a file that skips all rows except 1 and ...
Oracle中translate与replace的使用 - 数据库(内核) - 清泛网 - 专注C/C++及内核技术
Oracle中translate与replace的使用SELECT TRANSLATE(& 39;,abcdefghij,& 39;,& 39;,jabcdefghi& 39;,& 39;+& 39;) FROM dual; --第二、三参数一一对应，没有对应就删除原 SELECT TRANSLATE(',abc,', ',cab', '+') FROM dual; --结果：++
SELECT TRANSLATE(',abc,', 'cab,', '+') FROM dual; ...