My goal is just to use that SQL command but to traduct it from sqlite to mysql :
cursor.execute(f"SELECT count(*) FROM sqlite_master WHERE type='table' AND name='{ctx.guild.id}_counters'")
In MySQL things are different i saw that on internet so is there an equivalent of FROM sqlite_master that means FROM every table of the database in MySQL.
It would be something like this:
SELECT COUNT(*)
FROM information_schema.TABLES t
WHERE t.TABLE_NAME = 'myname'
information_schema is an internal MySQL database that has metadata about your databases. The TABLES and COLUMNS tables are probably of most interest to you.
Related
How can i count tables which starts with special prefix in MYSQL database?
I have below syntax below for showing table names which starts with prefix:
SHOW TABLES LIKE 'prefix\_%'
However i don't know how to count number of these tables.
I think below SQL useful to you.Change your database name and prefix value.
SELECT count(table_name) FROM information_schema.tables
WHERE table_type = 'base table' AND table_schema='database_name' AND table_name LIKE "prefix\_%";
Thank you.
I have 2 versions of a database (say db_dev and db_beta). I've made some changes in the db_dev database - added some tables, and changed a few columns in some existing tables. I need to find out the list of table names in which changes have been made.
I can easily find out the tables I've added by running the following query on the information_schema database:
SELECT table_name
FROM tables
WHERE table_schema = 'db_dev'
AND table_name NOT IN (SELECT table_name
FROM tables
WHERE table_schema = 'db_beta');
How do I get the table_names whose column_names do not match in the two database versions?
There are many ready made tools available which can give you changed schema by comparing two databases. Here are some tools which can serve your purpose :
Red-Gate's MySQL Schema & Data Compare
Maatkit
MySQL Diff
SQL EDT
Red-Gate's MySQL Compare is best tool for this purpose. Its paid though but they provide 14 days free trial version if you want to do something temporary.
Using information_schema, here is how it works.
First, you know that the information_schema.COLUMNS table contains the columns definition. If one column has been changed, or a table does not exist, it will reflect in the information_schema.COLUMNS table.
Difficult part is that you have to compare all columns of your COLUMNS table. So, you have to select TABLE_CATALOG,TABLE_NAME,COLUMN_NAME,ORDINAL_POSITION,COLUMN_DEFAULT, and so on (which is subject to evolution depending on your MySQL version).
The column list is the result of the following query:
SELECT GROUP_CONCAT(column_name)
FROM information_schema.COLUMNS
WHERE table_schema="information_schema"
AND table_name="COLUMNS" AND column_name!='TABLE_SCHEMA';
After that, we just have to SELECT TABLE_NAME, <column_list> and search for columns which appear once (column inexistent in other table), or where columns have two different definitions (columns altered). So we will have two different count in the resulting query to consider the two cases.
We will so use a prepared statement to retrieve the list of column we want, and grouping the result.
The resulting query does all the process for you:
SELECT CONCAT(
"SELECT DISTINCT TABLE_NAME
FROM information_schema.COLUMNS
WHERE TABLE_SCHEMA IN('db_dev', 'db_beta')
GROUP BY table_name, COLUMN_NAME
HAVING count(*)=1 OR
COUNT(DISTINCT CONCAT_WS(',', NULL, ",
GROUP_CONCAT(column_name)
,"))=2;")
FROM information_schema.COLUMNS
WHERE table_schema="information_schema"
AND table_name="COLUMNS" AND column_name!='TABLE_SCHEMA'
INTO #sql;
PREPARE stmt FROM #sql;
EXECUTE #sql;
The following solution does not use an sql query like you tried and does not give you a real list of tables, but it shows you all the changes in both databases.
You can do an sql dump of both database structures :
mysqldump -u root -p --no-data dbname > schema.sql
Then you can compare both files, e.g. using the diff linux tool.
Suppose I have a database data1 which gives me this:
show tables;
table1
table2
table3
Now instead of individually executing "select * from each table" i want to create a procedure which goes through each database shown in "show databases;" resultset, and then executes select * from each table of that database. I thought of using cursors which would scroll down the resultset, hold each database name in a variable and then execute select statement on each table of that database traversing in the same way. Can someone kindly help me out with how to use cursors in this case, as i am only aware of using cursors for SELECT and UPDATE statements.
btw i use MYSQL.
I'll refrain from asking why you would do this. Here is a general strategy in pseudocode;
[words in parentheses are (SQL commands and tables) which will run on your mySQL server.]
Connect to your mySQL server with your favourite tool/programming language and:
-- (USE information_schema;)
for db in (select distinct table_schema from tables;)
do:
for table in (select table_name from tables where table_schema='$db';)
do:
select field,column,attribute from $table;
done
done
Good luck!
you can get the query from infromation_Schema instead of 'show datbases'
Can you guys tell me how to fetch all the tables along with their records considering we don't know the table names in the database.
Such as :
use my_database
select * from information_schema.tables
-- gives all the tables from a database
Also it would be great if you can give mySQL and MSSQL queries.
I thought it would work but didn't work out:
select * from (select [TABLE_NAME] from INFORMATION_SCHEMA.TABLES)
For SQL Server you can use this:
exec sp_msforeachtable 'select * from ?'
I am working on a WPF application which installs if MySQL is installed,
so before installation I want to check whether mysql.proc table exists or not.
I googled about it and ended up with a query
select * from information_schema.Tables
where Table_schema = Schema() and Table_Name = 'mysql.proc'
This query returns an empty row.
I also tried simple select statement
select * from mysql.proc,
and this returned a table with the names of all the stored procedures, but if this table didn't exists then it throws an exception in the c# code.
So is there any way that I can fire a query from c# and get a boolean value depending on whether mysql.proc table exists or not?
Try SHOW TABLES FROM mysql LIKE 'proc'. If there are no result rows, the table doesn't exist. If there is one row, the table exists. Note that this approach isn't portable across RDBMSs, though that doesn't seem to be a concern of yours.
As for your first query, SCHEMA() returns the default database, so if it's not "mysql", the query will fail. Likewise, data in the Table_Name column doesn't include the database name, so comparing to 'mysql.proc' will always fail.