大约有 47,000 项符合查询结果（耗时：0.0306秒） [XML]
SQL SELECT speed int vs varchar
...k: A=261MB B=292MB C=322MB
Non-indexed by id: select count(*), select by id: 450ms same on all tables
Insert* one row per TX: B=9ms/record C=9ms/record
Bulk insert* in single TX: B=140usec/record C=180usec/record
Indexed by id, select by id: B=about 2...
Maximum number of characters using keystrokes A, Ctrl+A, Ctrl+C and Ctrl+V
...rate through for i up to n, doing two things: pressing A once and pressing select all + copy followed by paste j times (actually j-i-1 below; note the trick here: the contents are still in the clipboard, so we can paste it multiple times without copying each time). We only have to consider up to 4 c...
UITableViewCell subview disappears when cell is selected
I'm implementing a color-chooser table view where the user can select amongst, say, 10 colors (depends on the product). The user can also select other options (like hard drive capacity, ...).
...
PostgreSQL: How to pass parameters from command line?
...3="'2010-11-12'"
and then refer to the variables in sql as :v1, :v2 etc
select * from table_1 where id = :v1;
Please pay attention on how we pass string/date value using two quotes " '...' "
share
|
...
INSERT IF NOT EXISTS ELSE UPDATE?
...ike:
insert or replace into Book (ID, Name, TypeID, Level, Seen) values
((select ID from Book where Name = "SearchName"), "SearchName", ...);
Note that any field not in the insert list will be set to NULL if the row already exists in the table. This is why there's a subselect for the ID column: I...
How to change options of with jQuery?
Suppose a list of options is available, how do you update the <select> with new <option> s?
9 Answers
...
Oracle: If Table Exists
...
declare
c int;
begin
select count(*) into c from user_tables where table_name = upper('table_name');
if c = 1 then
execute immediate 'drop table table_name';
end if;
end;
That's for checking whether a table in the current schema exi...
Spring JPA selecting specific columns
...Spring JPA to perform all database operations. However I don't know how to select specific columns from a table in Spring JPA?
...
Ruby: Can I write multi-line string with no concatenation?
... HEREDOC syntax (via this link):
p <<END_SQL.gsub(/\s+/, " ").strip
SELECT * FROM users
ORDER BY users.id DESC
END_SQL
# >> "SELECT * FROM users ORDER BY users.id DESC"
The latter would mostly be for situations that required more flexibility in the processing. I personall...
psql - save results of command to a file
...peruser privileges and will write to a file on the server.
Example: COPY (SELECT foo, bar FROM baz) TO '/tmp/query.csv' (format csv, delimiter ';')
Creates a CSV file with ';' as the field separator.
As always, see the documentation for details
...