大约有 47,000 项符合查询结果(耗时:0.0272秒) [XML]
How do you create a read-only user in PostgreSQL?
I'd like to create a user in PostgreSQL that can only do SELECTs from a particular database. In MySQL the command would be:
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How to select date from datetime column?
...ry.
Use BETWEEN or >, <, = operators which allow to use an index:
SELECT * FROM data
WHERE datetime BETWEEN '2009-10-20 00:00:00' AND '2009-10-20 23:59:59'
Update: the impact on using LIKE instead of operators in an indexed column is high. These are some test results on a table with 1,...
What is the difference between HAVING and WHERE in SQL?
What is the difference between HAVING and WHERE in an SQL SELECT statement?
20 Answers
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How do I find numeric columns in Pandas?
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You could use select_dtypes method of DataFrame. It includes two parameters include and exclude. So isNumeric would look like:
numerics = ['int16', 'int32', 'int64', 'float16', 'float32', 'float64']
newdf = df.select_dtypes(include=numer...
How to save MySQL query output to excel or .txt file? [duplicate]
...SV file:
MySQL provides an easy mechanism for writing the results of a select
statement into a text file on the server. Using extended options of
the INTO OUTFILE nomenclature, it is possible to create a comma
separated value (CSV) which can be imported into a spreadsheet
application suc...
Selecting/excluding sets of columns in pandas [duplicate]
...e to create views or dataframes from an existing dataframe based on column selections.
9 Answers
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How to get the caret column (not pixels) position in a textarea, in characters, from the start?
...refox, Safari (and other Gecko based browsers) you can easily use textarea.selectionStart, but for IE that doesn't work, so you will have to do something like this:
function getCaret(node) {
if (node.selectionStart) {
return node.selectionStart;
} else if (!document.selection) {
return ...
Detect if value is number in MySQL
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This should work in most cases.
SELECT * FROM myTable WHERE concat('',col1 * 1) = col1
It doesn't work for non-standard numbers like
1e4
1.2e5
123. (trailing decimal)
share
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How to get sp_executesql result into a variable?
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DECLARE @ParmDefinition nvarchar(500);
DECLARE @tablename nvarchar(50)
SELECT @tablename = N'products'
SELECT @sSQL = N'SELECT @retvalOUT = MAX(ID) FROM ' + @tablename;
SET @ParmDefinition = N'@retvalOUT int OUTPUT';
EXEC sp_executesql @sSQL, @ParmDefinition, @retvalOUT=@retval OUTPUT;
SE...
MySQL: selecting rows where a column is null
I'm having a problem where when I try to select the rows that have a NULL for a certain column, it returns an empty set. However, when I look at the table in phpMyAdmin, it says null for most of the rows.
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