Is there an easy way to extract table DDL information, via a query, using either Ms or My SQL server? (preferably both?)
For example, using MySQL Administrator / Navicat for MySql, there is a "DDL" function, which generates the "create table foo (....)" script.
Is there any way to get this information from a query itself, such as:
Select DDL from foo where table_name='bar';
Any have the "Create table bar (.....)" returned to me?
If not - any suggestions?
it's mysql-specific, but SHOW CREATE TABLE <table-name> gives you the DDL for a table.
You have to create that yourself.
You can query INFORMATION_SCHEMA.COLUMNS for the column name and data type.
You can't get the CREATE Table text in a cross platform way, but you can get enough information to build it yourself from the INFORMATION_SCHEMA views.
Related
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'd like to know if it is possible to create an SQL function that will automatically update my View and add to it new tables in my DB.
My DB consist of multiple tables (same data structure) and are named as follow "MM_DD", now I would like to create a VIEW that joins all this data ( pretty simple , see query below) but I wish to automate the process so every time a new table is added the view will update.
CREATE OR REPLACE VIEW `viewTable` AS
select *,
md5(CONCAT(`columnA`,`columnB`)) AS myPK_id
from `05_06`
union all
select *,
md5(CONCAT(`columnA`,`columnB`)) AS myPK_id
from `05_08`
ect...
What I am doing at the moment is using PHP every time a table is added. It loops through the tables and create / update the view.
select * from information_schema.tables WHERE table_name LIKE '%05%'
Now that I have an array of table names -> create my Query string -> replace view...
Is this possible to do this in SQL?
If so, what is the correct approach?
Write a stored procedure to rebuild your view. You'll need to use what MySQL internally calls "prepared statements" so you can use string manipulation.
You'll still use your SELECT ... FROM information_schema.tables query to drive this stored procedure.
Once you get this working, you can embed it in a mySQL event, and arrange to run it automatically. For example, you could run it at the same time late at night.
Or, you can invoke the stored procedure immediately after you create one of these tables.
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.
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.
I'm trying to write a MySQL script that creates several tables. I have:
CREATE TABLE `DataBase1`.`tbl_this`(
...
);
CREATE TABLE `DataBase1`.`tbl_that`(
...
);
... (14 more) ...
BUT, only the first CREATE TABLE statement is executed. I get no syntax errors. Erm, am I missing the MSSQL equivalent of GO ? What am I doing wrong here; how do I get this baby to run all the tables?
How are you executing this script?
If you are trying to run it programmatically, you should know that the MySQL API only executes one statement at a time by default. You can't string them together with semicolons and expect it to run all the statements.
You can execute each CREATE TABLE statement individually in a loop, or else you can run a script by feeding it as input to the mysql command-line client.
It's not as easy as it would seem to write a general-purpose script runner class in your application, because the full script syntax include many corner cases.
See examples of the corner cases in my answer to Loading .sql files from within PHP.
The create table syntax looks fine. Probably the tool you use to execute your SQL just executes the first statement.
try this:
use database_name;
create table a..;
create table b..;
create table c..;
Are the tables referencing (e.g. primary keys and the like) one another? Tables are created serially, so if your second table is referencing a table that is not yet created, it will fail.
How do you execute your script ?
If you do it from command line it should be something like this:
mysql -u[username] -p[password] --database DataBase1 < scriptname.sql