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Oracle Differences between NVL and Coalesce
...n search contains comparison of nvl result with an indexed column.
create table tt(a, b) as
select level, mod(level,10)
from dual
connect by level<=1e4;
alter table tt add constraint ix_tt_a primary key(a);
create index ix_tt_b on tt(b);
explain plan for
select * from tt
where a=nvl(:1,a)
an...
How to set a Django model field's default value to a function call / callable (e.g., a date relative
...ow_add=True in the constructor, the datetime referenced by my_date is "immutable" (only set once when the row is inserted to the table).
With auto_now=True, however, the datetime value will be updated every time the object is saved.
This was definitely a gotcha for me at one point. For reference, ...
MySQL - length() vs char_length()
... 2 characters, even though like all combining marks it can — if a suitable font is available — be rendered as a single glyph. UTF-16LE can still have a 4-byte character though thanks to the surrogates.
– bobince
Nov 14 '09 at 22:05
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Algorithm to find top 10 search terms
...ue ID for each. This whole set of data can be loaded into memory as a hash table, consuming roughly 300MB memory. (We have implemented our own hash table. The Java's implementation takes huge memory overhead)
Each phrase then can be identified as an array of integers.
This is important, because s...
How do I use an INSERT statement's OUTPUT clause to get the identity value?
...wly inserted ID being output to the SSMS console like this:
INSERT INTO MyTable(Name, Address, PhoneNo)
OUTPUT INSERTED.ID
VALUES ('Yatrix', '1234 Address Stuff', '1112223333')
You can use this also from e.g. C#, when you need to get the ID back to your calling app - just execute the SQL query wi...
How do I use LINQ Contains(string[]) instead of Contains(string)
...ids = arrayofuids.Select(id => int.Parse(id)).ToList();
var selected = table.Where(t => uids.Contains(t.uid));
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What is the fastest integer division supporting division by zero no matter what the result is?
...y accessible in C through using idiom. That is why it so hard to make a portable multiple precision integer library in C without resorting to (inline) assembly. My guess is that most decent compilers will understand the above idiom.
Another way of avoiding branches, as also remarked in some of the ...
How do I represent a hextile/hex grid in memory?
...u/~amitp/game-programming/grids (the diagrams are for square grids but the table includes the formulas for axial hex grids also)
– amitp
Jun 7 '13 at 0:58
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How to declare an array in Python?
... while some extra space
insert operation is expensive
Check this awesome table of operations complexity.
Also, please see this picture, where I've tried to show most important differences between array, array of references and linked list:
...
Create an empty data.frame
...
You could use read.table with an empty string for the input text as follows:
colClasses = c("Date", "character", "character")
col.names = c("Date", "File", "User")
df <- read.table(text = "",
colClasses = colClasses,
...