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MySQL Conditional Insert
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If your DBMS does not impose limitations on which table you select from when you execute an insert, try:
INSERT INTO x_table(instance, user, item)
SELECT 919191, 123, 456
FROM dual
WHERE NOT EXISTS (SELECT * FROM x_table
WHE...
HTML table with fixed headers?
Is there a cross-browser CSS/JavaScript technique to display a long HTML table such that the column headers stay fixed on-screen and do not scroll with the table body. Think of the "freeze panes" effect in Microsoft Excel.
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Difference between one-to-many and many-to-one relationship
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From this page about Database Terminology
Most relations between tables are one-to-many.
Example:
One area can be the habitat of many readers.
One reader can have many subscriptions.
One newspaper can have many subscriptions.
A Many to One relation is the same as o...
Multiple select statements in Single query
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SELECT (
SELECT COUNT(*)
FROM user_table
) AS tot_user,
(
SELECT COUNT(*)
FROM cat_table
) AS tot_cat,
(
SELECT COUNT(*)
FROM course_table
) AS tot_course
share
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Adding a new SQL column with a default value
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Try this:
ALTER TABLE table1 ADD COLUMN foo INT DEFAULT 0;
From the documentation that you linked to:
ALTER [ONLINE | OFFLINE] [IGNORE] TABLE tbl_name
alter_specification [, alter_specification] ...
alter_specification:
...
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Postgresql - change the size of a varchar column to lower length
I have a question about the ALTER TABLE command on a really large table (almost 30 millions rows).
One of its columns is a varchar(255) and I would like to resize it to a varchar(40) .
Basically, I would like to change my column by running the following command:
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How do you copy a record in a SQL table but swap out the unique id of the new row?
...es close to what I need, but my scenario is slightly different. The source table and destination table are the same and the primary key is a uniqueidentifier (guid). When I try this:
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Convert Rows to columns using 'Pivot' in SQL Server
I have read the stuff on MS pivot tables and I am still having problems getting this correct.
8 Answers
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Physical vs. logical / soft delete of database record?
...and you don't have to worry about cascading a delete through various other tables in the database that reference the row you are deleting. Disadvantage is that you have to code any reporting/display methods to take the flag into account.
As far as if it is a common practice - I would say yes, but ...
How to find foreign key dependencies in SQL Server?
... all Foreign Key Relationships within the current database.
SELECT
FK_Table = FK.TABLE_NAME,
FK_Column = CU.COLUMN_NAME,
PK_Table = PK.TABLE_NAME,
PK_Column = PT.COLUMN_NAME,
Constraint_Name = C.CONSTRAINT_NAME
FROM
INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS C
INNER JOIN INF...