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MySQL error: key specification without a key length
...d, and the trick is to choose a number N that’s long enough to give good selectivity, but short enough to save space. The prefix should be long enough to make the index nearly as useful as it would be if you’d indexed the whole column.
Before we go further let us define some important terms. In...
Trigger change() event when setting 's value with val() function
... easiest and best way to trigger change event when setting the value of select element.
5 Answers
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How do you set the startup page for debugging in an ASP.NET MVC application?
...he start page property.
Go to the project's Properties
Go to the Web tab
Select the Specific Page radio button
Type in the desired url in the Specific Page text box
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T-SQL query to show table definition?
...n get most of the details from Information Schema Views and System Views.
SELECT ORDINAL_POSITION, COLUMN_NAME, DATA_TYPE, CHARACTER_MAXIMUM_LENGTH
, IS_NULLABLE
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = 'Customers'
SELECT CONSTRAINT_NAME
FROM INFORMATION_SCHEMA.CONSTRAINT_TABLE_US...
How do I delete a fixed number of rows with sorting in PostgreSQL?
...
You could try using the ctid:
DELETE FROM logtable
WHERE ctid IN (
SELECT ctid
FROM logtable
ORDER BY timestamp
LIMIT 10
)
The ctid is:
The physical location of the row version within its table. Note that although the ctid can be used to locate the row version very quickly,...
JPA and Hibernate - Criteria vs. JPQL or HQL
...oaded. This means one Criteria query might result in several SQL immediate SELECT statements to fetch the subgraph with all non-lazy mapped associations and collections. If you want to change the "how" and even the "what", use setFetchMode() to enable or disable outer join fetching for a particular ...
“CASE” statement within “WHERE” clause in SQL Server 2008
...
Try the following:
select * From emp_master
where emp_last_name=
case emp_first_name
when 'test' then 'test'
when 'Mr name' then 'name'
end
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Using “like” wildcard in prepared statement
...place("[", "![");
PreparedStatement pstmt = con.prepareStatement(
"SELECT * FROM analysis WHERE notes LIKE ? ESCAPE '!'");
pstmt.setString(1, notes + "%");
or a suffix-match:
pstmt.setString(1, "%" + notes);
or a global match:
pstmt.setString(1, "%" + notes + "%");
...
How to migrate/convert from SVN to Mercurial (hg) on windows
...made
much simpler: Start the TortoiseHG
Workbench from the Start menu. Select
File --> Settings. Select Extensions
from the list. Check the 'convert'
checkbox and click OK. That's it! No
need to try to generate the config
file anymore and search it in the file
system. – bgever M...
Modifying a subset of rows in a pandas dataframe
...The df.A==0 expression creates a boolean series that indexes the rows, 'B' selects the column. You can also use this to transform a subset of a column, e.g.:
df.loc[df.A==0, 'B'] = df.loc[df.A==0, 'B'] / 2
I don't know enough about pandas internals to know exactly why that works, but the basic is...