大约有 37,000 项符合查询结果（耗时：0.0325秒） [XML]
Subset of rows containing NA (missing) values in a chosen column of a data frame
...t "NA" strings to NA values, and let "NULL" strings as is).
If using read.table() or read.csv(), you should consider the "na.strings" argument to do clean data import, and always work with real R NA values.
An example, working in both cases "NULL" and "NA" cells :
DF <- read.csv("file.csv", na...
SQL - Select first 10 rows only?
...
In SQL server, use:
select top 10 ...
e.g.
select top 100 * from myTable
select top 100 colA, colB from myTable
In MySQL, use:
select ... order by num desc limit 10
share
|
improve this ...
How do you manually execute SQL commands in Ruby On Rails using NuoDB
...n.execute("foo")
with "foo" being the sql statement( i.e. "SELECT * FROM table").
This command will return a set of values as a hash and put them into the results variable.
So on my rails application_controller.rb I added this:
def execute_statement(sql)
results = ActiveRecord::Base.connectio...
JSP tricks to make templating easier?
...Files (and the Stripes framework, that's the s: tags..). This results in a table of rows, alternating colors, page navigation, etc:
<t:table items="${actionBean.customerList}" var="obj" css_class="display">
<t:col css_class="checkboxcol">
<s:checkbox name="customerIds" value="$...
Is it a good idea to index datetime field in mysql?
.... In my application I will have many rows for example I currently have one table with 4 million records. Most of my queries use datetime clause to select data. Is it a good idea to index datetime fields in mysql database?
...
SQL Server 2012 column identity increment jumping from 6 to 1000+ on 7th entry [duplicate]
...ork for hosted Sql Server Express installations. So, I created an identity table, and use this through an INSTEAD OF trigger. I'm hoping this helps someone else, and/or gives others an opportunity to improve my solution. The last line allows returning the last identity column added. Since I typicall...
Rails new vs create
...fferently.
An HTTP GET to /resources/new is intended to render a form suitable for creating a new resource, which it does by calling the new action within the controller, which creates a new unsaved record and renders the form.
An HTTP POST to /resources takes the record created as part of the ne...
Select something that has more/less than x character
...L Server, Use the LEN (Length) function:
SELECT EmployeeName FROM EmployeeTable WHERE LEN(EmployeeName) > 4
MSDN for it states:
Returns the number of characters of the specified string expression,
excluding trailing blanks.
Here's the link to the MSDN
For oracle/plsql you can use Leng...
How to list active / open connections in Oracle?
Is there any hidden table, system variable or something to show active connections in a given moment?
9 Answers
...
ERROR: permission denied for sequence cities_id_seq using Postgres
...
Interesting. I did a GRANT all on the table that my sequence is in, but this doesn't seem to cover the sequence. This also seems to very by OS.
– Kinnard Hockenhull
Jun 7 '14 at 15:48
...