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What is cardinality in MySQL?
...ow cardinality column with only 2 possible values as the index will not be selective enough to be used.
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Which are more performant, CTE or temporary tables?
...(A INT IDENTITY PRIMARY KEY, B INT , F CHAR(8000) NULL);
INSERT INTO T(B)
SELECT TOP (1000000) 0 + CAST(NEWID() AS BINARY(4))
FROM master..spt_values v1,
master..spt_values v2;
Example 1
WITH CTE1 AS
(
SELECT A,
ABS(B) AS Abs_B,
F
FROM T
)
SELECT *
FROM CTE1
WHERE A = 780
...
PostgreSQL Crosstab Query
... - not fit for missing attributes
crosstab(text) with 1 input parameter:
SELECT *
FROM crosstab(
'SELECT section, status, ct
FROM tbl
ORDER BY 1,2' -- needs to be "ORDER BY 1,2" here
) AS ct ("Section" text, "Active" int, "Inactive" int);
Returns:
Section | Active | Inacti...
How can mixed data types (int, float, char, etc) be stored in an array?
...minated union, aka tagged union.
struct {
enum { is_int, is_float, is_char } type;
union {
int ival;
float fval;
char cval;
} val;
} my_array[10];
The type member is used to hold the choice of which member of the union is should be used for each array element. ...
Is there a way to specify how many characters of a string to print out using printf()?
Is there a way to specify how many characters of a string to print out (similar to decimal places in int s)?
8 Answers
...
Conveniently Declaring Compile-Time Strings in C++
...y cumbersome, as the string needs to be declared as a variadic sequence of characters, e.g.
15 Answers
...
How to read a CSV file into a .NET Datatable
...e(path);
string fileName = Path.GetFileName(path);
string sql = @"SELECT * FROM [" + fileName + "]";
using(OleDbConnection connection = new OleDbConnection(
@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + pathOnly +
";Extended Properties=\"Text;HDR=" + h...
Fetch the row which has the Max value for a column
... multiple rows for the userid where the maximum date is on multiple rows.
select userid,
my_date,
...
from
(
select userid,
my_date,
...
max(my_date) over (partition by userid) max_my_date
from users
)
where my_date = max_my_date
"Analytic functions rock"
Edi...
convert a char* to std::string
...g to store data retrieved by fgets() . To do this I need to convert the char* return value from fgets() into an std::string to store in an array. How can this be done?
...
uint8_t can't be printed with cout
...
It doesn't really print a blank, but most probably the ASCII character with value 5, which is non-printable (or invisible). There's a number of invisible ASCII character codes, most of them below value 32, which is the blank actually.
You have to convert aa to unsigned int to output t...