大约有 40,000 项符合查询结果（耗时：0.0460秒） [XML]
How to use GROUP BY to concatenate strings in MySQL?
...
SELECT id, GROUP_CONCAT(name SEPARATOR ' ') FROM table GROUP BY id;
http://dev.mysql.com/doc/refman/5.0/en/group-by-functions.html#function_group-concat
From the link above, GROUP_CONCAT: This function returns a string res...
Order a MySQL table by two columns
...h query not working in my case.. Tn this case, I dont get sorting for City select distinct City, Country from customers order by Country desc, City desc;
– Pra_A
Sep 15 '16 at 6:55
...
Unable to export Apple production push SSL certificate in .p12 format
...
Turns out all you have to do is select "My Certificates" on the left panel and it enables the .p12 option.
share
|
improve this answer
|
...
How do MySQL indexes work?
...be faster to go through the pages one by one (in a database, this is "poor selectivity").
For a 10-page book, it makes no sense to make an index, as you may end up with a 10-page book prefixed by a 5-page index, which is just silly - just scan the 10 pages and be done with it.
The index also needs t...
How does the SQL injection from the “Bobby Tables” XKCD comic work?
..., the parenthesis makes more sense with an INSERT. Thinking backwards, the SELECT would not run anyway as the Insert of the Little Bobby Tables in the table would have already dropped the table.
– ypercubeᵀᴹ
Jan 21 '13 at 21:41
...
How to copy a selection to the OS X clipboard
I have an area selected in Vim. How can I copy it into the OS X clipboard?
27 Answers
...
How to add column if not exists on PostgreSQL?
...s, _col text, _type regtype)
RETURNS bool AS
$func$
BEGIN
IF EXISTS (SELECT 1 FROM pg_attribute
WHERE attrelid = _tbl
AND attname = _col
AND NOT attisdropped) THEN
RETURN FALSE;
ELSE
EXECUTE format('ALTER TABLE %s ADD COLUMN %I %s...
How can I get enum possible values in a MySQL database?
... This solution works on codeigniter github.com/thiswolf/codeigniter-enum-select-boxes
– You Know Nothing Jon Snow
Jul 7 '13 at 16:28
3
...
Remove the last character in a string in T-SQL?
... ELSE LEFT(@String, LEN(@String) - 1)
END
) END
SELECT @String
share
|
improve this answer
|
follow
|
...
What columns generally make good indexes?
...earching 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 columns should be indexed against which yo...