Is it possible to use the create table query (create table t2 like t1) to get the query instead the actual table? Kind of like duplicating some management consoles Send To editor feature?
I think you're looking for SHOW CREATE TABLE tablename;
'tablename' can be the table within the current database, if you've selected one, or you can qualify it as in 'dbname.tablename'. The output can be used to create the table again. In fact, I sometimes use it in scripts that need to either use an existing table or create it if it doesn't exist. First I'll get the table creation info as shown above, and then I'll use something like"
CREATE TABLE IF NOT EXISTS tablename .........
Where '..........' is all the goodies that SHOW CREATE TABLE tablename gives me.
If you're interested in a good tutorial on MySQL (the database), as well as SQL (the language), you might have a look at the O'Reilly book, Learning MySQL. It's pretty good.
Related
Right now, I'm altering a table with a crap ton of data, which is going to take weeks to run. In the meantime, I figured I'd create a new table to write to while this one is locked.
I can create an empty table and just write to this one, and check both tables when reading. Or I can create a copy of the current table and do all reads/writes from this copy for the next month.
It looks like copying the table is not the best solution. What about creating a view (just to read from) combining both tables?
CREATE VIEW MY_TABLE_VIEW AS
SELECT * FROM MY_TABLE
UNION ALL
SELECT * FROM MY_TABLE_COPY
Would creating the view be just as expensive as altering the original table? Should I instead just change all my table reads to UNION ALL the results from both tables?
Creating a view is a metadata-only operation. Views don't store any data. Querying the view will actually query the base table as if you ran the query in the view definition. So there's practically nothing to do to create the view. It only stores the query as metadata.
I'm rather new at database management, so this might not be feasible, but I got a handful of SQL select queries, rather long ones at that. What I'd like is to get the table column names and structure, without access to the actual database, so as to get a map of all this queries.
context: All we have are the queries used to output tables that will be given to us latter.
This need not be done with actual SQL code, maybe a short script in other language or a utility somebody knows of (but I do have MySQL workbench)
You can add a CREATE TABLE statement in front of your select queries to get the column names.
You cannot infer data types or keys from select queries.
For column names do something like:
drop table if exists your_table_name;
create table your_table_name
select *
from ...
where the select * portion is replaced by the select queries you have.
Then to see the column names in a friendlier way you can do:
show create table your_table_name;
or
desc your_table_name;
I want to replicate certain table from one database into another database in the same server. This tables contain exactly the same fields.
I was considering to use MySQL Replication to replicate that table but some people said that it will increase IO so i find another way to create 3 Trigger (Insert, update and Delete) that will perform exactly the same thing like what i expect.
My Question is, which way is better? Is it using MySQL replication is better even though it's in the same server or using Trigger to replicate the data is better.
Thanks.
I don't know what is your goal, but I got mine getting use of the VIEW functionality.
I had two different applications with separate databases but in the same Mysql server. Application2 needed to get a few data from Application1. In general, this is a trivial situation that you can handle with USE DB1; or USE DB2; as your needing, but my programming framework does not work very well with multiple DBs.
So, lets see my solution...
Here is my select query to retrieve this data:
SELECT id, name FROM DB1.customers;
So, using DB2 as default schema, I've created a VIEW:
USE DB2;
CREATE VIEW app1_customers AS SELECT id, name FROM DB1.customers;
Now I can retrieve this data in DB2 as a regular table with a regular SELECT statement.
SELECT * FROM DB2.app1_customers;
Hope ts useful. BR
Assuming you have two databases on the same server i.e DB1 and DB2 and the table is called tbl1 and it is sitting in DB1 you can query the table like this:
USE DB1;
SELECT * FROM tbl1;
USE DB2;
SELECT * FROM DB1.tbl1;
This way you wont need to copy the data and worry about extra space and extra code. You can query a table in another database on the same server. Replication and triggers are not your answer here. You could also create a view to encapsulate the SQL statement.
Definitely triggers is the way to go. Having another server (slave) will need to spare several MB for installation, logs, cpu and memory usage.
I'd use triggers to keep both tables equal. If you want to create a table with the same columns definition and data use:
USE db2;
CREATE TABLE t1 AS SELECT * FROM db1.t1;
After that, go ahead and create the triggers for Update, Insert and Delete statemetns.
Also you could ALTER the new table to a different engine like MEMORY or add indexes to see if you can improve something.
For example, I have a table named movies. It has the fields/columns title VARCHAR(100) and runtime INT(5). It's loaded with 10,000 rows of data.
I want to create another table, let's call it movies_custom, that has all of the same columns, but with none of the data.
Is there a quick SQL statement to do this?
EDIT: Sorry, I noticed the SQL Server tag on this and assumed that was the technology you were using until I saw MySQL in the question title.
You can use the syntax CREATE movies_custom LIKE movies in MySQL
Sure!
In SQL Server you can do this query:
select top 0 * into movies_custom from movies
That creates the table structure without inserting any rows.
Very easy in MySQL:
CREATE newtable LIKE oldtable;
The other answers led me in the right direction, but I had to add the keyword TABLE in order to make it work with MySQL Workbench 6.
CREATE TABLE movies_custom LIKE movies;
Is there a way to do this?
In case the DBMS command history got cleaned or, in my case, when many ALTER TABLE were used in the course of time.
I'm using MySQL.
Yes, it is as simple as
SHOW CREATE TABLE yourtable;
This will include all the subsequent ALTER TABLE statements. You cannot retrieve the table's original state.
Here is the relevant documentation