大约有 41,000 项符合查询结果（耗时：0.0513秒） [XML]
Select where count of one field is greater than one
...clause, for aggregate result comparison.
Taking the query at face value:
SELECT *
FROM db.table
HAVING COUNT(someField) > 1
Ideally, there should be a GROUP BY defined for proper valuation in the HAVING clause, but MySQL does allow hidden columns from the GROUP BY...
Is this in preparati...
How to get value of selected radio button?
I want to get the selected value from a group of radio buttons.
28 Answers
28
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Python nonlocal statement
...eavily indented when defining inner functions and ends up violating the 79 chars PEP8 recommendation. Any way to get around this problem? Can an inner function somehow be placed outside the outer function? I know the question sounds stupid, but I'm earnest.
– tommy.carstensen
...
What is this operator in MySQL?
...d <> both give UNKNOWN with NULL on either side of the expression.)
SELECT *
FROM table
WHERE YourColumn IS NOT NULL;
can also negate the null safe equality operator but this is not standard SQL.
SELECT *
FROM table
WHERE NOT (YourColumn <=> NULL);
...
Is there a way to access the “previous row” value in a SELECT statement?
...d to order by some column for this to be meaningful. Something like this:
select t1.value - t2.value from table t1, table t2
where t1.primaryKey = t2.primaryKey - 1
If you know how to order things but not how to get the previous value given the current one (EG, you want to order alphabetically) ...
Xcode variables
...
Ok, so when I use char* cv = getenv("CURRENT_VARIANT"); I get NULL. What am I missing?
– Brooks
Dec 31 '13 at 16:06
1
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What is size_t in C?
...array index.
Depending on the implementation, it can be any of:
unsigned char
unsigned short
unsigned int
unsigned long
unsigned long long
Here's how size_t is defined in stddef.h of my machine:
typedef unsigned long size_t;
...
What does the “__block” keyword mean?
...c NSInteger CounterStatic;
{
NSInteger localCounter = 42;
__block char localCharacter;
void (^aBlock)(void) = ^(void) {
++CounterGlobal;
++CounterStatic;
CounterGlobal = localCounter; // localCounter fixed at block creation
localCharacter = 'a'; // sets ...
how to emulate “insert ignore” and “on duplicate key update” (sql merge) with postgresql?
... two queries, one for INSERT and one for UPDATE (as an appropriate join/subselect of course - no need to write your main filter twice)
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Are PDO prepared statements sufficient to prevent SQL injection?
....
$pdo->query('SET NAMES gbk');
$var = "\xbf\x27 OR 1=1 /*";
$query = 'SELECT * FROM test WHERE name = ? LIMIT 1';
$stmt = $pdo->prepare($query);
$stmt->execute(array($var));
In certain circumstances, that will return more than 1 row. Let's dissect what's going on here:
Selecting a Cha...