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Studies on optimal code width?
...ght Margin" in your IDE of choice, it is likely that it will default to 80 characters. I tend to change it to 120 for no reason other than it was the standard at a company I was with a few years back, and no other company has told me to do it differently.
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Join vs. sub-query
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@JinghuiNiu Customers who bought expensive items: select custid from cust join bought using (custid) where price > 500. If a customer bought multiple expensive items, you'll get double-ups. To fix this, select custid from cust where exists (select * from bought where cust...
How to select the row with the maximum value in each group
In a dataset with multiple observations for each subject I want to take a subset with only the maximum data value for each record. For example, with a following dataset:
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Does the join order matter in SQL?
...t matter. The queries will return same results, as long as you change your selects from SELECT * to SELECT a.*, b.*, c.*.
For (LEFT, RIGHT or FULL) OUTER joins, yes, the order matters - and (updated) things are much more complicated.
First, outer joins are not commutative, so a LEFT JOIN b is no...
Clear form field after select for jQuery UI Autocomplete
I'm developing a form, and using jQuery UI Autocomplete. When the user selects an option, I want the selection to pop into a span appended to the parent <p> tag. Then I want the field to clear rather than be populated with the selection.
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What are the Ruby Gotchas a newbie should be warned about? [closed]
...as constants, so local variables should begin with a lowercase letter.
The characters $ and @ do not indicate variable data type as in Perl, but rather function as scope resolution operators.
To denote floating point numbers, one must follow with a zero digit (99.0) or an explicit conversion (99.to_...
Professional jQuery based Combobox control? [closed]
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If I already select one value, then click arrow it only show the selected value, not all value.
– linbo
Oct 10 '12 at 11:55
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How to create a trie in Python
...a linear search. But the search would be limited to the number of possible characters -- 27 if we include _end. Also, there's nothing to be gained by creating a massive list of nodes and accessing them by index as he suggests; you might as well just nest the lists.
Finally, I'll add that creating a...
What is a bus error?
...*/
int main() {
int fd;
int *map;
int size = sizeof(int);
char *name = "/a";
shm_unlink(name);
fd = shm_open(name, O_RDWR | O_CREAT, (mode_t)0600);
/* THIS is the cause of the problem. */
/*ftruncate(fd, size);*/
map = mmap(NULL, size, PROT_READ | PROT_WRITE, MA...
Are nested transactions allowed in MySQL?
...Y) ENGINE=InnoDB;
START TRANSACTION;
INSERT
INTO t_test
VALUES (1);
SELECT *
FROM t_test;
id
---
1
SAVEPOINT tran2;
INSERT
INTO t_test
VALUES (2);
SELECT *
FROM t_test;
id
---
1
2
ROLLBACK TO tran2;
SELECT *
FROM t_test;
id
---
1
ROLLBACK;
SELECT *
FROM ...