My current application was built up in SQL Server 2008 server in JAVA with Hibernate and I had used HierarchyId data type for department hierarchy in my database.
I had written SQL queries to deal with HierarchyId datatype. And I also have n-Level of department tree structure.
Now I want to change my Database server from SQL Server 2008 to MySQL as per business requirement.
After feasibility checking I came with the solution that my whole application will migrate to MySQL database server except HierarchyId data type.
So my main challenge is to find alternate solution of HierarchyId data type with the minimal change in coding.
What is the best way to implement department hierarchy in my database?
Thanks...
I faced the similar situation when our team decided to migrate from MS-SQL to MySQL. We resolved the issue using the following steps:
Added a column of type varchar(100) to the same table in MS SQL.
Converted the hierarchyid from hexadecimal value to string using the hierarchyid.ToString() function as saved it in the newly created column using computed column functionality. for eg. 0x58 -> "/1/", 0x7CE0 -> "/3/7/".
The level of the entity is equal to no-of '/''s minus 1.
These columns could be migrated to the MySQL.
The IsDesendantOf() and is method was replaced with LIKE function of string concaenated with '%'.
Thus we got rid of the hierarchyid functionality in MySQL.
Whenever we face such an issue, we just need to ask ourselves, what would we have done if this functionality would not have been provided by the tool we use. We generally end up getting the answer optimally.
Mysql has no equivalent that I'm aware of, but you could store the same data in a varchar.
For operations involving the HierarchyId, you're probably going to have to implement them yourself, probably as either user defined functions or stored procedures.
What sqlserver does looks like the "materialized path" method of storing a hierarchy. One example of that in mysql can be seen at http://www.cloudconnected.fr/2009/05/26/trees-in-sql-an-approach-based-on-materialized-paths-and-normalization-for-mysql/
I am migrating a database from Sql Server 2008 to Teradata
and I am facing a problem:
In Sql Server in the ddl of a table column is defined as follows:
[rowguid] uniqueidentifier ROWGUIDCOL NOT NULL CONSTRAINT [DF_Address_rowguid] DEFAULT (NEWID())
This column uses newid() function to generate and insert random varchar value in the column [rowguid] if the user doesnt provide any input.
There is no similar function in Teradata to generate this value.
What can be used instead of of NEWID() function of Sql Server while creating similar table ddls for Teradata?
There is no native equivalent for a GUID/UUID in Teradata. Teradata does offer an IDENTITY column to provide an auto-incrementing column. The IDENTITY column does not come without its own nuances and I would encourage you to read the Chapter 5 - Create Table in the SQL Data Definition Language - Detailed Topics which has a section explaining Identity Columns.
However, as part of your migration from SQL Server to Teradata you will need to understand the concept of how data is distributed in Teradata by means of the table's primary index. This may require that you review your existing data model and re-engineer how it is physically implemented in Teradata.
Is there a difference between a schema and a database in MySQL? In SQL Server, a database is a higher level container in relation to a schema.
I read that Create Schema and Create Database do essentially the same thing in MySQL, which leads me to believe that schemas and databases are different words for the same objects.
As defined in the MySQL Glossary:
In MySQL, physically, a schema is synonymous with a database. You can substitute the keyword SCHEMA instead of DATABASE in MySQL SQL syntax, for example using CREATE SCHEMA instead of CREATE DATABASE.
Some other database products draw a distinction. For example, in the Oracle Database product, a schema represents only a part of a database: the tables and other objects owned by a single user.
Depends on the database server. MySQL doesn't care, its basically the same thing.
Oracle, DB2, and other enterprise level database solutions make a distinction. Usually a schema is a collection of tables and a Database is a collection of schemas.
Refering to MySql documentation,
CREATE DATABASE creates a database with the given name. To use this
statement, you need the CREATE privilege for the database. CREATE
SCHEMA is a synonym for CREATE DATABASE as of MySQL 5.0.2.
PostgreSQL supports schemas, which is a subset of a database:
https://www.postgresql.org/docs/current/static/ddl-schemas.html
A database contains one or more named schemas, which in turn contain
tables. Schemas also contain other kinds of named objects, including
data types, functions, and operators. The same object name can be used
in different schemas without conflict; for example, both schema1 and
myschema can contain tables named mytable. Unlike databases, schemas
are not rigidly separated: a user can access objects in any of the
schemas in the database they are connected to, if they have privileges
to do so.
Schemas are analogous to directories at the operating system level, except that schemas cannot be nested.
In my humble opinion, MySQL is not a reference database. You should never quote MySQL for an explanation. MySQL implements non-standard SQL and sometimes claims features that it does not support. For example, in MySQL, CREATE schema will only create a DATABASE. It is truely misleading users.
This kind of vocabulary is called "MySQLism" by DBAs.
in MySQL schema is synonym of database.
Its quite confusing for beginner people who jump to MySQL and very first day find the word schema, so guys nothing to worry as both are same.
When you are starting MySQL for the first time you need to create a database (like any other database system) to work with so you can CREATE SCHEMA which is nothing but CREATE DATABASE
In some other database system schema represents a part of database or a collection of Tables, and collection of schema is a database.
Yes, people use these terms interchangeably with regard to MySQL. Though oftentimes you will hear people inappropriately refer to the entire database server as the database.
Simply if you are thinking or discussing about Mysql. Then take a simple answer
"SCHEMA & DATABASE are exactly the same thing, just a synthetic
sugar in mysql."
Just add some more info:
MongoDB also distinguish schema from database.
schema represent the tables, which means the structure of database.
Microsoft SQL Server for instance, Schemas refer to a single user and is another level of a container in the order of indicating the server, database, schema, tables, and objects.
For example, when you are intending to update dbo.table_a and the syntax isn't full qualified such as
UPDATE table.a the DBMS can't decide to use the intended table. Essentially by default the DBMS will utilize myuser.table_a
not like Postgres, SQL server schema is set of database have same thing
but in mysql schema and database it is the same
MySQL does not support the concept of schema. In MySQL, schema and schemas are synonyms for database and databases.
When a user connects to MySQL, they don't connect to a specific database. Instead, they can access any table they have permissions for
I'm getting data from an MSSQL DB ("A") and inserting into a MySQL DB ("B") using the date created in the MSSQL DB. I'm doing it with simple logics, but there's got to be a faster and more efficient way of doing this. Below is the sequence of logics involved:
Create one connection for MSSQL DB and one connection for MySQL DB.
Grab all of data from A that meet the date range criterion provided.
Check to see which of the data obtained are not present in B.
Insert these new data into B.
As you can imagine, step 2 is basically a loop, which can easily max out the time limit on the server, and I feel like there must be a way of doing this must faster and during when the first query is made. Can anyone point me to right direction to achieve this? Can you make "one" connection to both of the DBs and do something like below?
SELECT * FROM A.some_table_in_A.some_column WHERE
"it doesn't exist in" B.some_table_in_B.some_column
A linked server might suit this
A linked server allows for access to distributed, heterogeneous
queries against OLE DB data sources. After a linked server is created,
distributed queries can be run against this server, and queries can
join tables from more than one data source. If the linked server is
defined as an instance of SQL Server, remote stored procedures can be
executed.
Check out this HOWTO as well
If I understand your question right, you're just trying to move things in the MSSQL DB into the MySQL DB. I'm also assuming there is some sort of filter criteria you're using to do the migration. If this is correct, you might try using a stored procedure in MSSQL that can do the querying of the MySQL database with a distributed query. You can then use that stored procedure to do the loops or checks on the database side and the front end server will only need to make one connection.
If the MySQL database has a primary key defined, you can at least skip step 3 ("Check to see which of the data obtained are not present in B"). Use INSERT IGNORE INTO... and it will attempt to insert all the records, silently skipping over ones where a record with the primary key already exists.
I have a dataset with a lot of columns I want to import into a MySQL database, so I want to be able to create tables without specifying the column headers by hand. Rather I want to supply a filename with the column labels in it to (presumably) the MySQL CREATE TABLE command. I'm using standard MySQL Query Browser tools in Ubuntu, but I didn't see in option for this in the create table dialog, nor could I figure out how to write a query to do this from the CREATE TABLE documentation page. But there must be a way...
A CREATE TABLE statement includes more than just column names
Table name*
Column names*
Column data types*
Column constraints, like NOT NULL
Column options, like DEFAULT, character set
Table constraints, like PRIMARY KEY* and FOREIGN KEY
Indexes
Table options, like storage engine, default character set
* mandatory
You can't get all this just from a list of column names. You should write the CREATE TABLE statement yourself.
Re your comment: Many software development frameworks support ways to declare tables without using SQL DDL. E.g. Hibernate uses XML files. YAML is supported by Rails ActiveRecord, PHP Doctrine and Perl's SQLFairy. There are probably other tools that use other format such as JSON, but I don't know one offhand.
But eventually, all these "simplified" interfaces are no less complex to learn as SQL, while failing to represent exactly what SQL does. See also The Law of Leaky Abstractions.
Check out SQLFairy, because that tool might already convert from files to SQL in a way that can help you. And FWIW MySQL Query Browser (or under its current name, MySQL Workbench) can read SQL files. So you probably don't have to copy & paste manually.