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How do MySQL indexes work?
...be faster to go through the pages one by one (in a database, this is "poor selectivity").
For a 10-page book, it makes no sense to make an index, as you may end up with a 10-page book prefixed by a 5-page index, which is just silly - just scan the 10 pages and be done with it.
The index also needs t...
Comparing Dates in Oracle SQL
...r by using the built-in TO_DATE() function, or a date literal.
TO_DATE()
select employee_id
from employee
where employee_date_hired > to_date('31-DEC-95','DD-MON-YY')
This method has a few unnecessary pitfalls
As a_horse_with_no_name noted in the comments, DEC, doesn't necessarily mean D...
How do you display code snippets in MS Word preserving format and syntax highlighting?
...d install Notepad++ and do the following:
Paste your code in the window;
Select the programming language from the language menu;
Select the text to copy;
Right click and select Plugin commands -> Copy Text with Syntax Highlighting;
Paste it into MS Word and you are good to go!
Update 29/06/20...
What makes a SQL statement sargable?
...non-sargable is to include a field inside a function in the where clause:
SELECT ... FROM ...
WHERE Year(myDate) = 2008
The SQL optimizer can't use an index on myDate, even if one exists. It will literally have to evaluate this function for every row of the table. Much better to use:
WHERE myDat...
“Wrap with try…catch” in IntelliJ?
Can I select a block of code and have IntelliJ wrap it with a "try...catch" ?
9 Answers
...
LINQ to SQL Left Outer Join
...table), where-as yours matches only 0-1. To do a left outer join, you need SelectMany and DefaultIfEmpty, for example:
var query = from c in db.Customers
join o in db.Orders
on c.CustomerID equals o.CustomerID into sr
from x in sr.DefaultIfEmpty()
s...
IntelliJ: Viewing diff of all changed files between local and a git commit/branch
... new UI, click on Show Diff with Working Tree
Next a window will pop up. Select Files and press cmd + d
Another window which shows diff. You can perform many different types of diff. Use cmd + shift + ] and cmd + shift + [ to shift between files.
Diff Tip: IntelliJ provides advanced diff feat...
What is the difference between UNION and UNION ALL?
...want the duplicates (especially when developing reports).
UNION Example:
SELECT 'foo' AS bar UNION SELECT 'foo' AS bar
Result:
+-----+
| bar |
+-----+
| foo |
+-----+
1 row in set (0.00 sec)
UNION ALL example:
SELECT 'foo' AS bar UNION ALL SELECT 'foo' AS bar
Result:
+-----+
| bar |
+---...
How to select html nodes by ID with jquery when the id contains a dot?
...
@Tomalak in comments:
since ID selectors must be preceded by a hash #, there should be no ambiguity here
“#id.class” is a valid selector that requires both an id and a separate class to match; it's valid and not always totally redundant.
The correct...
XPath - Selecting elements that equal a value
In Xpath, I am wanting to select elements that equal a specific value.
2 Answers
2
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