大约有 40,000 项符合查询结果（耗时：0.0378秒） [XML]
What columns generally make good indexes?
...portant role in query optimization and searching the results speedily from tables. So it is most important step to select which columns to be indexed. There are two major places where we can consider indexing: columns referenced in the WHERE clause and columns used in JOIN clauses. In short, such co...
How to convert boost path type to string?
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@MarcoAlka See the linked table boost.org/doc/libs/1_48_0/libs/filesystem/v3/doc/… and note the second line: class path canonize() Function removed - that means it was once in the library but no longer--the definition of deprecated.
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How does std::forward work? [duplicate]
...thing using another mysterious thing. This particular cast is defined by a table in Xeo's answer. But the question is: Why? So here's my understanding:
Suppose I want to pass you an std::vector<T> v that you're supposed to store in your data structure as data member _v. The naive (and safe) s...
How to select multiple rows filled with constants?
Selecting constants without referring to a table is perfectly legal in an SQL statement:
15 Answers
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Why does C++11 not support designated initializer lists as C99? [closed]
...me it has failed
Ben Voigt's comments have helped me to see the insurmountable problems with this approach; given:
struct X {
int c;
char a;
float b;
};
What order would these functions be called in in c99: struct X foo = {.a = (char)f(), .b = g(), .c = h()}? Surprisingly, in c99:
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Create table in SQLite only if it doesn't exist already
I want to create a table in a SQLite database only if doesn't exist already. Is there any way to do this? I don't want to drop the table if it exists, only create it if it doesn't.
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How to convert a table to a data frame
I have a table in R that has str() of this:
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How can I get the SQL of a PreparedStatement?
...ke this:
org.hsqldb.jdbc.JDBCPreparedStatement@7098b907[sql=[INSERT INTO
TABLE_NAME(COLUMN_NAME, COLUMN_NAME, COLUMN_NAME) VALUES(?, ?, ?)],
parameters=[[value], [value], [value]]]
Now I've created a method (Java 8), which is using regex to extract both query and values and put them into map:
p...
How do MySQL indexes work?
...ically, how can they return the data requested without scanning the entire table?
8 Answers
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TSQL Pivot without aggregate function
I have a table like this...
9 Answers
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