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Rails: Adding an index after adding column
Suppose I created a table table in a Rails app. Some time later, I add a column running:
5 Answers
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Is there any significant difference between using if/else and switch-case in C#?
... in debug or compatibility mode. In release, it will be compiled into jump table (through MSIL 'switch' statement)- which is O(1).
C# (unlike many other languages) also allows to switch on string constants - and this works a bit differently. It's obviously not practical to build jump tables for str...
Retrieving the last record in each group - MySQL
There is a table messages that contains data as shown below:
27 Answers
27
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Want to find records with no associated records in Rails
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Just imagine you have 10000000 records in friends table. What about performance in that case?
– goodniceweb
Dec 20 '16 at 14:51
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How to check if a column exists in a SQL Server table?
...HERE Name = N'columnName'
AND Object_ID = Object_ID(N'schemaName.tableName'))
BEGIN
-- Column Exists
END
Martin Smith's version is shorter:
IF COL_LENGTH('schemaName.tableName', 'columnName') IS NOT NULL
BEGIN
-- Column Exists
END
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How to read the database table name of a Model instance?
Given a model's instance object, how can I get the database table's name?
1 Answer
1
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Set NOW() as Default Value for datetime datatype?
I have two columns in table users namely registerDate and lastVisitDate which consist of datetime data type. I would like to do the following.
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App Inventor Tutorials and Examples: Dynamic Table Layout | Pura Vida Apps
...vacy Policy Contact Dynamic Table Layout and Table Listpicker Thank you Christopher for being the sponsor of the App Inventor 2 version! It was asked in the App Inventor Forum, how to display a table in App Inventor without knowing how m...
Possible to perform cross-database queries with PostgreSQL?
...them.
postgres_fdw
Use postgres_fdw (foreign data wrapper) to connect to tables in any Postgres database - local or remote.
Note that there are foreign data wrappers for other popular data sources. At this time, only postgres_fdw and file_fdw are part of the official Postgres distribution.
For P...
How to append rows to an R data frame
...O I come with 4 distinct solutions:
rbindlist to the data.frame
Use data.table's fast set operation and couple it with manually doubling the table when needed.
Use RSQLite and append to the table held in memory.
data.frame's own ability to grow and use custom environment (which has reference seman...