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What's the fastest way to merge/join data.frames in R?
... posted in the question, it might appear that indexes were used on the two tables but, in fact, they are placed on tables which were overwritten before the sql select ever runs and that, in part, accounts for why its so slow. The idea of sqldf is that the data frames in your R session constitute th...
What is a proper naming convention for MySQL FKs?
...tically.
In any case, this is the convention that I use:
fk_[referencing table name]_[referenced table name]_[referencing field name]
Example:
CREATE TABLE users(
user_id int,
name varchar(100)
);
CREATE TABLE messages(
message_id int,
user_id int
);
ALTER TABLE me...
Why not use tables for layout in HTML? [closed]
It seems to be the general opinion that tables should not be used for layout in HTML.
66 Answers
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How do I create a SQL table under a different schema?
...
Right-click on the tables node and choose New Table...
With the table designer open, open the properties window (view -> Properties Window).
You can change the schema that the table will be made in by choosing a schema in the properties wind...
MySQL Cannot Add Foreign Key Constraint
... as a project requirement and it worked the first time or two on different tables, but I have two tables on which I get an error when trying to add the Foreign Key Constraints.
The error message that I get is:
...
Copy tables from one database to another in SQL Server
I have a database called foo and a database called bar. I have a table in foo called tblFoobar that I want to move (data and all) to database bar from database foo. What is the SQL statement to do this?
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insert a NOT NULL column to an existing table
...
As an option you can initially create Null-able column, then update your table column with valid not null values and finally ALTER column to set NOT NULL constraint:
ALTER TABLE MY_TABLE ADD STAGE INT NULL
GO
UPDATE MY_TABLE SET <a valid not null values for your column>
GO
ALTER TABLE MY_TA...
Saving changes after table edit in SQL Server Management Studio
If I want to save any changes in a table, previously saved in SQL Server Management Studio (no data in table present) I get an error message:
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SELECT INTO using Oracle
...
If NEW_TABLE already exists then ...
insert into new_table
select * from old_table
/
If you want to create NEW_TABLE based on the records in OLD_TABLE ...
create table new_table as
select * from old_table
/
If the purpose is...
How to see the values of a table variable at debug time in T-SQL?
Can we see the values (rows and cells) in a table valued variable in SQL Server Management Studio (SSMS) during debug time? If yes, how?
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