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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...
How to get a value from a cell of a dataframe?
...
Most answers are using iloc which is good for selection by position.
If you need selection-by-label loc would be more convenient.
For getting a value explicitly (equiv to deprecated
df.get_value('a','A'))
# this is also equivalent to df1.at['a','A']
In [55]: df1....
How to clear variables in ipython?
...r @ErdemKAYA comment.
To erase a variable, use the magic command:
%reset_selective <regular_expression>
The variables that are erased from the namespace are the one matching the given <regular_expression>.
Therefore
%reset_selective -f a
will erase all the variables containing a...
Values of disabled inputs will not be submitted
...lements support the disabled attribute: BUTTON, INPUT,
OPTGROUP, OPTION, SELECT, and TEXTAREA.
This attribute is inherited but local declarations override the
inherited value.
How disabled elements are rendered depends on the user agent. For
example, some user agents "gray out" disab...
Oracle中translate与replace的使用 - 数据库(内核) - 清泛网 - 专注C/C++及内核技术
Oracle中translate与replace的使用SELECT TRANSLATE(& 39;,abcdefghij,& 39;,& 39;,jabcdefghi& 39;,& 39;+& 39;) FROM dual; --第二、三参数一一对应，没有对应就删除原 SELECT TRANSLATE(',abc,', ',cab', '+') FROM dual; --结果：++
SELECT TRANSLATE(',abc,', 'cab,', '+') FROM dual; ...
Repeat each row of data.frame the number of times specified in a column
...es
library(dplyr)
df %>%
slice(rep(seq_len(n()), freq)) %>%
select(-freq)
# var1 var2
#1 a d
#2 b e
#3 b e
#4 c f
#5 c f
#6 c f
seq_len(n()) part can be replaced with any of the following.
df %>% slice(rep(1:nrow(df), freq)) %>% select(-...
Excel Date to String conversion
...ard. It's found under the Data tab in Excel 2007.
If you have one column selected, the defaults for file type and delimiters should work, then it prompts you to change the data format of the column. Choosing text forces it to text format, to make sure that it's not stored as a date.
...
How can I run just the statement my cursor is on in SQL Server Management Studio?
...
Use Ctrl+KU to select a line.
Then use F5 to run it.
Although it only works for single line selection, still I find it quite useful.
Hope it helps!!
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How to output MySQL query results in CSV format?
...ech-recipes.com/rx/1475/save-mysql-query-results-into-a-text-or-csv-file/
SELECT order_id,product_name,qty
FROM orders
WHERE foo = 'bar'
INTO OUTFILE '/var/lib/mysql-files/orders.csv'
FIELDS TERMINATED BY ','
ENCLOSED BY '"'
LINES TERMINATED BY '\n';
Using this command columns names will not be e...
How to generate a create table script for an existing table in phpmyadmin?
...o view full query
There is this Hyperlink named +Options left above, There select Full Texts
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