大约有 37,000 项符合查询结果（耗时：0.0341秒） [XML]
MySQL: multiple tables or one table with many columns?
... user has one name and password), then it's probably better to have it one table, since it reduces the number of joins the database will need to do to retrieve results. I think some databases have a limit on the number of columns per table, but I wouldn't worry about it in normal cases, and you can ...
HTML table td meaning
In HTML table, what does td stands for? I mean literally, what is it acronym for? Table division? Table data?
8 Answers
...
Centering text in a table in Twitter Bootstrap
For some reason, The text inside the table still is not centered. Why? How do I center the text inside the table?
10 Answer...
How to reset AUTO_INCREMENT in MySQL?
...
You can reset the counter with:
ALTER TABLE tablename AUTO_INCREMENT = 1
For InnoDB you cannot set the auto_increment value lower or equal to the highest current index. (quote from ViralPatel):
Note that you cannot reset the counter to a value less than or ...
What is the difference between “INNER JOIN” and “OUTER JOIN”?
... the outer parts of a Venn diagram union.
Examples
Suppose you have two tables, with a single column each, and data as follows:
A B
- -
1 3
2 4
3 5
4 6
Note that (1,2) are unique to A, (3,4) are common, and (5,6) are unique to B.
Inner join
An inner join using either of the...
How do I temporarily disable triggers in PostgreSQL?
...ly, if you are wanting to disable all triggers, not just those on the USER table, you can use:
SET session_replication_role = replica;
This disables triggers for the current session.
To re-enable for the same session:
SET session_replication_role = DEFAULT;
Source: http://koo.fi/blog/2013/01...
SQL query to find record with ID not in another table
I have two tables with binding primary key in database and I desire to find a disjoint set between them. For example,
6 Ans...
What is SYSNAME data type in SQL Server?
... be honest. It is mainly used by Microsoft when building the internal sys tables and stored procedures etc within SQL Server.
For example, by executing Exec sp_help 'sys.tables' you will see that the column name is defined as sysname this is because the value of this is actually an object in itsel...
Join between tables in two different databases?
...ccount has appropriate permissions you can use:
SELECT <...>
FROM A.table1 t1 JOIN B.table2 t2 ON t2.column2 = t1.column1;
You just need to prefix the table reference with the name of the database it resides in.
sha...
Select multiple columns in data.table by their numeric indices
...ltiple columns using a vector of their numeric indices (position) in data.table ?
5 Answers
...