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Alter MySQL table to add comments on columns
...
Script for all fields on database:
SELECT
table_name,
column_name,
CONCAT('ALTER TABLE `',
TABLE_SCHEMA,
'`.`',
table_name,
'` CHANGE `',
column_name,
'` `',
column_name,
'` ',
column_typ...
How to select the nth row in a SQL database table?
I'm interested in learning some (ideally) database agnostic ways of selecting the n th row from a database table. It would also be interesting to see how this can be achieved using the native functionality of the following databases:
...
How do I rename a column in a database table using SQL?
...any other RDBMS), you can do it with regular ALTER TABLE statement:
=> SELECT * FROM Test1;
id | foo | bar
----+-----+-----
2 | 1 | 2
=> ALTER TABLE Test1 RENAME COLUMN foo TO baz;
ALTER TABLE
=> SELECT * FROM Test1;
id | baz | bar
----+-----+-----
2 | 1 | 2
...
Remove all spaces from a string in SQL Server
...
Simply replace it;
SELECT REPLACE(fld_or_variable, ' ', '')
Edit:
Just to clarify; its a global replace, there is no need to trim() or worry about multiple spaces for either char or varchar:
create table #t (
c char(8),
v varchar(8))...
Possible to perform cross-database queries with PostgreSQL?
... executes a query in a remote database
dblink executes a query (usually a SELECT, but it can be any SQL
statement that returns rows) in a remote database.
When two text arguments are given, the first one is first looked up as
a persistent connection's name; if found, the command is executed on
that...
PostgreSQL Autoincrement
...RT INTO foo (bar) values ('blah');
INSERT INTO foo (bar) values ('blah');
SELECT * FROM foo;
1,blah
2,blah
SERIAL is just a create table time macro around sequences. You can not alter SERIAL onto an existing column.
sha...
Location of my.cnf file on macOS
...m there, MySQLWorkbench can create them for you by:
Opening a connection
Selecting the 'Options File' under 'INSTANCE' in the menu.
MySQLWorkbench will search for my.cnf and if it can't find it, it'll create it for you
sh...
Check if table exists without using “select from”
Is there a way to check if a table exists without selecting and checking values from it?
17 Answers
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Is there any performance gain in indexing a boolean field?
...
It depends on the actual queries and the selectivity of the index/query combination.
Case A: condition WHERE isok = 1 and nothing else there:
SELECT *
FROM tableX
WHERE isok = 1
If the index is selective enough (say you have 1M rows and only 1k have isok = 1), ...
Inserting a Python datetime.datetime object into MySQL
...
when iserting into t-sql
this fails:
select CONVERT(datetime,'2019-09-13 09:04:35.823312',21)
this works:
select CONVERT(datetime,'2019-09-13 09:04:35.823',21)
easy way:
regexp = re.compile(r'\.(\d{6})')
def to_splunk_iso(dt):
"""Converts the datetime ...