大约有 40,000 项符合查询结果（耗时：0.0332秒） [XML]
What version of Visual Studio is Python on my computer compiled with?
...
Where does this table come from?
– Glyph
Aug 20 '12 at 0:30
5
...
Remove duplicated rows
...
The data.table package also has unique and duplicated methods of it's own with some additional features.
Both the unique.data.table and the duplicated.data.table methods have an additional by argument which allows you to pass a chara...
What is the difference between a schema and a table and a database?
...bably a n00blike (or worse) question. But I've always viewed a schema as a table definition in a database. This is wrong or not entirely correct. I don't remember much from my database courses.
...
How to do a batch insert in MySQL
I have 1-many number of records that need to be entered into a table. What is the best way to do this in a query? Should I just make a loop and insert one record per iteration? Or is there a better way?
...
Oracle find a constraint
...stem generated constraint name. For instance, if we specify NOT NULL in a table declaration. Or indeed a primary or unique key. For example:
SQL> create table t23 (id number not null primary key)
2 /
Table created.
SQL> select constraint_name, constraint_type
2 from user_constraint...
Make column not nullable in a Laravel migration
I'm writing a migration to make certain columns in a table nullable right now. For the down function, I of course want to make those columns not nullable again. I looked through the schema builder docs , but couldn't see a way to do this.
...
Import SQL file into mysql
I have a database called nitm . I haven't created any tables there. But I have a SQL file which contains all the necessary data for the database. The file is nitm.sql which is in C:\ drive . This file has size of about 103 MB. I am using wamp server.
...
Ways to save enums in database
...g.
But if you wanted to really do that, i would create a Suits dimension table:
| Suit | SuitID | Rank | Color |
|------------|--------------|---------------|--------|
| Unknown | 4 | 0 | NULL |
| Heart | 1 | 1 | Red ...
Assign multiple columns using := in data.table, by group
What is the best way to assign to multiple columns using data.table ? For example:
2 Answers
...
How to understand nil vs. empty vs. blank in Ruby
...
I made this useful table with all the cases:
blank?, present? are provided by Rails.
share
|
improve this answer
|
...