In this post, I am sharing two different scripts to populate attach and detach scripts for all your SQL Server Databases.

When we are migrating our SQL Database Server, we require to move all databases from one server to another server.

If you have a big number of databases, making of individual attach and detach script will take more time.

I have also added script to change database access mode like: Multi_User to Single_User for Detach Process and Single_User to Multi_User for Attach Process.

If your database is in use, you may require to change the database access mode to close all running connections.

Using this script you can populate attach and detach scripts for all databases.
Execute this script to generate detach scripts for all databases:

DECLARE @DatabaseName AS VARCHAR(255)
DECLARE CurDetach CURSOR FOR
  
  SELECT name
  FROM   MASTER.sys.databases
  WHERE  owner_sid > 1;

OPEN CurDetach
FETCH Next FROM CurDetach INTO @DatabaseName
WHILE @@FETCH_STATUS = 0
  BEGIN      
	  PRINT 
		'ALTER DATABASE ' + @DatabaseName + ' SET SINGLE_USER WITH ROLLBACK IMMEDIATE' 
		+ CHAR(10) + ' GO' + CHAR(10) +
		'sp_detach_db ' + @DatabaseName + CHAR(10)
		+ ' GO' + CHAR(10) + 'Print ''Detach of '
		+ @DatabaseName
		+ ' database completed successfully'''
		+ CHAR(10) + ' GO'

      FETCH NEXT FROM CurDetach INTO @DatabaseName
  END

CLOSE CurDetach
DEALLOCATE CurDetach

Execute this script to generate attach scripts for all databases:
You can change your file name or file path using @Filepath variable.

DECLARE @DatabaseName AS VARCHAR(255)
DECLARE @Filepath AS VARCHAR(255)

SET @Filepath = 'C:\SQLDATA\'

DECLARE CurAttach CURSOR FOR
  SELECT name
  FROM   MASTER.sys.databases
  WHERE  owner_sid > 1;

OPEN CurAttach
FETCH Next FROM CurAttach INTO @DatabaseName
WHILE @@FETCH_STATUS = 0
  BEGIN      
	  PRINT 
		'CREATE DATABASE ' + @DatabaseName + ' ON
		(FILENAME = '+ @Filepath + @DatabaseName +'.mdf)
		,(FILENAME = '+ @Filepath + @DatabaseName +'.ldf)
		FOR ATTACH
		GO

		ALTER DATABASE '+ @DatabaseName +' SET MULTI_USER WITH ROLLBACK IMMEDIATE
		GO'
      FETCH NEXT FROM CurAttach INTO @DatabaseName
  END

CLOSE CurAttach
DEALLOCATE CurAttach

In this post, I am sharing a kind of utility article which you can use to export your records or data from SQL Server Database to Windows Text File.

Let me share, where I am using this. I am monitoring the performance of a few critical stored procedures by logging in line important messages.

Later, I am saving this details into a text file and sending that text file as an email attachment. We can also directly send table data as an email body, but we require into files for other tools also.

You can use xp_cmdshell and BCP command to export your data from SQL Server to Text File.
If you are getting an error like below, enable xp_cmdshell. You can use below reference article to enable xp_cmdshell.

Msg 15281, Level 16, State 1, Procedure xp_cmdshell, Line 1
SQL Server blocked access to procedure 'sys.xp_cmdshell' of component 'xp_cmdshell' because this component is turned off as part of the security configuration for this server. 
A system administrator can enable the use of 'xp_cmdshell' by using sp_configure. For more information about enabling 'xp_cmdshell', search for 'xp_cmdshell' in SQL Server Books Online.

SQL Server: Script to Enable and Disable XP_CMDSHELL Configuration

Create a table with sample data:

CREATE TABLE tbl_Students
(
	Rno INT PRIMARY KEY
	,STudName VARCHAR(20)
	,ClassName CHAR(1)
)
GO

INSERT INTO tbl_Students 
VALUES 
(1,'Anvesh','A'),(2,'Neevan','B'),(3,'Toby','C')
,(5,'Roy','A'),(4,'Jenny','B'),(6,'Kaviy','C')
,(7,'Martin','A'),(8,'Laxmi','B'),(9,'Nion','C')
GO

Execute xp_cmdshell to export data in text file:

EXEC xp_cmdshell 'bcp "SELECT * FROM dbo.tbl_Students" queryout "C:\Test\StudentData.txt" -T -c -t,'

Check the text file:

Recently, I shared one article on PostgreSQL schemas migration.

PostgreSQL: Script to copy Table Data from one Schema to another Schema

The migration activities are very common for all DBAs. I found lots of different questions on migration exercises.
In this post, I am sharing a Linux shell script to copy your table data from one PostgreSQL Server to another PostgreSQL Server using psql command line.

I am just migrating the data; please create a blank table at your destination/second database server.

This is a utility script. Further, you can modify the script for generic use something like by adding parameters for host_name, database_name, table_name and others

Linux Bash Shell Script for data migration between PostgreSQL Servers:

#!/bin/bash
psql \
    -X \
    -U user_name \
    -h host_name1 \
    -d database_name \
    -c "\\copy tbl_Students to stdout" \
| \
psql \
    -X \
    -U user_name \
    -h host_name2 \
    -d database_name \
    -c "\\copy tbl_Students from stdin"

You can also filter the column list something like below script:

#!/bin/bash
psql \
    -X \
    -U user_name \
    -h host_name1 \
    -d database_name \
    -c "\\copy (SELECT Rno, Studname FROM tbl_Students) to stdout" \
| \
psql \
    -X \
    -U user_name \
    -h host_name2 \
    -d database_name \
    -c "\\copy tbl_Students from stdin"

In this post, I am sharing one option to Disable / Enable the Foreign Key Constraint in PostgreSQL.

During data migration and testing purpose, Database Developer requires to disable Foreign key constraint of a Table.

Once you disable constraint, then later you might need to enable again, but during this exercise make sure that all your data changes are correct.

PostgreSQL does not provide any direct command or function to disable / enable the Foreign key constraints.

When you create any Foreign Key on the table, internally It creates a hidden trigger for check data integrity.
You should enable/disable the trigger for achieving disable foreign key constraint.

Create a sample Student Master table:

CREATE TABLE tbl_Students 
(
	StudID INTEGER PRIMARY KEY
	,StudName CHARACTER VARYING
	,StudClass CHAR(1)	
);

Insert few sample records in Student Master table:

INSERT INTO tbl_Students 
VALUES (1,'Anvesh','A')
,(2,'Neevan','B'),(3,'Jenny','C')
,(4,'Roy','C'),(5,'Martin','C');

Create a sample Student Marks table:

CREATE TABLE tbl_StudentMarks
(
	StudentMarkID INTEGER PRIMARY KEY
	,StudID INTEGER 
	,Sub1Mark SMALLINT
	,Sub2Mark SMALLINT
	,Sub3Mark SMALLINT	
	,CONSTRAINT fk_tbl_StudentMarks_StudID FOREIGN KEY (StudID) REFERENCES tbl_Students (StudID)
);

Try to insert data with StudID which does not belong to Student Master table:

INSERT INTO tbl_StudentMarks 
VALUES (1,6,50,60,90);

You will get a below error message:

ERROR:  insert or update on table "tbl_studentmarks" violates foreign key constraint "fk_tbl_studentmarks_studid"
DETAIL:  Key (studid)=(6) is not present in table "tbl_students".
********** Error **********

Disable all hidden triggers of a Student Mark table:

ALTER TABLE tbl_StudentMarks DISABLE TRIGGER ALL;

Now Again, try to insert same record:

INSERT INTO tbl_StudentMarks 
VALUES (1,6,50,60,90);

Once you did with your task, please enable all trigger of a table:

ALTER TABLE tbl_StudentMarks ENABLE TRIGGER ALL;

During the migration activity, most of the time we are facing issues related to Case Sensitivity.
For example,

In Windows Operating System, you cannot create two different directories like: “DBrnd.Com” and “dbrnd.com”. This both consider as same name in Windows Operating System, but In Linux Operating System, You can create both directories separately like: “DBrnd. Com” and “dbrnd.com”.

When we are migrating MySQL Database between two different Operating Systems, we should also take care about the name of Database files and folders.

There are mainly two MySQL Server parameters lower_case_file_system and lower_case_table_names.

A lower_case_file_system parameter ensures about case sensitivity of file names on the file system where the data directory is located.
A lower_case_file_system OFF means file names are Case Sensitive, and ON means file names are Case Insensitive.

A lower_case_table_names parameters ensure about case sensitivity of table names.
If lower_case_table_names = 0, Table name stored as specified, but comparisons are Case Sensitive.
If lower_case_table_names = 1, Table name stored in lower case and comparisons are not Case Sensitive.
If lower_case_table_names = 2, Table name stored as specified, but comparisons are in Lowercase.