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How to create a MySQL hierarchical recursive query
... or self-joins.
MySQL 8+
with recursive cte (id, name, parent_id) as (
select id,
name,
parent_id
from products
where parent_id = 19
union all
select p.id,
p.name,
p.parent_id
from products p
inner join cte
...
半个汉字的校验与处理(C++) - C/C++ - 清泛网 - 专注C/C++及内核技术
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// strSrc: 原始字符串
// nMaxLen: 截断后的最大长度
char *GetTruncate(char *strSrc, int nMaxLen)
{
if (strSrc == NULL || nMaxLen == 0)
{
return NULL;
}
int len = strlen(strSrc);
if (len == 0)
{
...
How do I select an entire row which has the largest ID in the table?
...
You could use a subselect:
SELECT row
FROM table
WHERE id=(
SELECT max(id) FROM table
)
Note that if the value of max(id) is not unique, multiple rows are returned.
If you only want one such row, use @MichaelMior's answer,
SELEC...
(-2147483648> 0) returns true in C++?
...
@RichardJ.RossIII - with clang you are probably getting a 64-bit-typed literal, since it was too big to fit in an int. OP's implementation may not have a 64-bit type.
– Carl Norum
Feb 4 '1...
Difference between EXISTS and IN in SQL?
...way to avoid counting:
--this statement needs to check the entire table
select count(*) from [table] where ...
--this statement is true as soon as one match is found
exists ( select * from [table] where ... )
This is most useful where you have if conditional statements, as exists can be a lot ...
Should I use static_cast or reinterpret_cast when casting a void* to whatever
...g between pointer types (as is fairly common when indexing in memory via a char*, for example), static_cast will generate a compiler error and you'll be forced to use reinterpret_cast anyway.
In practice I use reinterpret_cast because it's more descriptive of the intent of the cast operation. You c...
Passing an array to a query using a WHERE clause
...y external input is sanitized.
$ids = join("','",$galleries);
$sql = "SELECT * FROM galleries WHERE id IN ('$ids')";
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how do i remove a comma off the end of a string?
...sponding ltrim for left trim) is very useful as you can specify a range of characters to remove, i.e. to remove commas and trailing whitespace you would write:
$string = rtrim($string, ", \t\n");
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How do I get extra data from intent on Android?
...TRING);
getArguments().getBoolean(ARG_SECTION_BOOL);
getArguments().getChar(ARG_SECTION_CHAR);
getArguments().getByte(ARG_SECTION_DATA);
}
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What is the “N+1 selects problem” in ORM (Object-Relational Mapping)?
The "N+1 selects problem" is generally stated as a problem in Object-Relational mapping (ORM) discussions, and I understand that it has something to do with having to make a lot of database queries for something that seems simple in the object world.
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