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data.table vs dplyr: can one do something well the other can't or does poorly?
... ## data.table syntax
left_join(DT2, DT1) ## dplyr syntax
# 2. select columns while join
DT1[DT2, .(z, i.mul)]
left_join(select(DT2, x, y, mul), select(DT1, x, y, z))
# 3. aggregate while join
DT1[DT2, .(sum(z) * i.mul), by = .EACHI]
DF1 %>% group_by(x, y) %>% summarise(z = su...
SQL server query to get the list of columns in a table along with Data types, NOT NULL, and PRIMARY
...licate rows for some columns, use user_type_id instead of system_type_id.
SELECT
c.name 'Column Name',
t.Name 'Data type',
c.max_length 'Max Length',
c.precision ,
c.scale ,
c.is_nullable,
ISNULL(i.is_primary_key, 0) 'Primary Key'
FROM
sys.columns c
INNER JOIN
...
Google Play Services Library update and missing symbol @integer/google_play_services_version
...
control click -> properties -> android -> libraries, add -> select the project you just imported -> ok
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How to save CSS changes of Styles panel of Chrome Developer Tools?
...oper Tools, Right-click in the left panel (where the files are listed) and select Add Folder to Workspace. You can get to a stylesheet in the Sources panel quickly by clicking the stylesheet at the top-right of each CSS rule for a selected element in the Elements panel.
After adding the folder,...
Cannot drop database because it is currently in use
...ar(50)
SET @DatabaseName = N'YOUR_DABASE_NAME'
DECLARE @SQL varchar(max)
SELECT @SQL = COALESCE(@SQL,'') + 'Kill ' + Convert(varchar, SPId) + ';'
FROM MASTER..SysProcesses
WHERE DBId = DB_ID(@DatabaseName) AND SPId <> @@SPId
--SELECT @SQL
EXEC(@SQL)
...
How do I create a ListView with rounded corners in Android?
...
It doesn't work well with selection-highlighting though: When top or bottom item is selected, it's colored background is rectangular and drawn on top of the round-cornered background.
– Kris Van Bael
Jul 27 '11 a...
MySQL OPTIMIZE all tables?
...>.<your_table>;, optimize all tables in a given schema like this: select concat('OPTIMIZE NO_WRITE_TO_BINLOG TABLE ',table_schema,'.',table_name,';') into outfile '/tmp/optimize_all_tables.sql' from information_schema.tables where table_schema = 'pabeta' and table_type = 'base table'; sourc...
MySQL/Amazon RDS error: “you do not have SUPER privileges…”
...e “Parameter Groups” tab.
Create a new Parameter Group. On the dialog, select the MySQL family compatible to your MySQL database version, give it a name and confirm.
Select the just created Parameter Group and issue “Edit Parameters”.
Look for the parameter ‘log_bin_trust_function_creators...
How to delete a row by reference in data.table?
...el.idxs' vs. 'keep.idxs'
keep.idxs <- setdiff(DT[, .I], del.idxs); # select row indexes to keep
cols = names(DT);
DT.subset <- data.table(DT[[1]][keep.idxs]); # this is the subsetted table
setnames(DT.subset, cols[1]);
for (col in cols[2:length(cols)]) {
DT.subset[, (col) := DT[...
Postgresql query between date ranges
... things become simpler if you use >= start AND < end.
For example:
SELECT
user_id
FROM
user_logs
WHERE
login_date >= '2014-02-01'
AND login_date < '2014-03-01'
In this case you still need to calculate the start date of the month you need, but that should be straight forw...