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Adding 'serial' to existing column in Postgres
...int, b text);
CREATE TABLE bar (a serial, b text);
INSERT INTO foo (a, b) SELECT i, 'foo ' || i::text FROM generate_series(1, 5) i;
INSERT INTO bar (b) SELECT 'bar ' || i::text FROM generate_series(1, 5) i;
-- blocks of commands to turn foo into bar
CREATE SEQUENCE foo_a_seq;
ALTER TABLE foo ALTER...
Finding duplicate values in a SQL table
...
SELECT
name, email, COUNT(*)
FROM
users
GROUP BY
name, email
HAVING
COUNT(*) > 1
Simply group on both of the columns.
Note: the older ANSI standard is to have all non-aggregated columns in the GROUP BY ...
Difference between two dates in MySQL
...
SELECT TIMEDIFF('2007-12-31 10:02:00','2007-12-30 12:01:01');
-- result: 22:00:59, the difference in HH:MM:SS format
SELECT TIMESTAMPDIFF(SECOND,'2007-12-30 12:01:01','2007-12-31 10:02:00');
-- result: 79259 the differenc...
SQL select only rows with max value on a column [duplicate]
...ce...
All you need is a GROUP BY clause with the MAX aggregate function:
SELECT id, MAX(rev)
FROM YourTable
GROUP BY id
It's never that simple, is it?
I just noticed you need the content column as well.
This is a very common question in SQL: find the whole data for the row with some max value ...
Counting the number of option tags in a select tag in jQuery
How do I count the number of <option> s in a <select> DOM element using jQuery?
8 Answers
...
Selecting data from two different servers in SQL Server
How can I select data in the same query from two different databases that are on two different servers in SQL Server?
15 An...
How to concatenate columns in a Postgres SELECT?
... an explicit coercion to text [...]
Bold emphasis mine. The 2nd example (select a||', '||b from foo) works for any data types since the untyped string literal ', ' defaults to type text making the whole expression valid in any case.
For non-string data types, you can "fix" the 1st statement by c...
Get all table names of a particular database by SQL query?
...different sql dbms deal with schemas.
Try the following
For SQL Server:
SELECT TABLE_NAME
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_TYPE = 'BASE TABLE' AND TABLE_CATALOG='dbName'
For MySQL:
SELECT TABLE_NAME
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_TYPE = 'BASE TABLE' AND TABLE_SCHEMA='dbN...
How to create a listbox in HTML without allowing multiple selection?
...eate a simple listbox, but one of the requirements is to DISALLOW multiple selection. Most of the code for listboxes goes like this -
...
Insert Update trigger how to determine if insert or update
... track "before" and "after" data. So you can use something like IF EXISTS (SELECT * FROM DELETED) to detect an update. You only have rows in DELETED on update, but there are always rows in INSERTED.
Look for "inserted" in CREATE TRIGGER.
Edit, 23 Nov 2011
After comment, this answer is only for INSER...