Tampilkan postingan dengan label Sybase and SQL Server. Tampilkan semua postingan
Tampilkan postingan dengan label Sybase and SQL Server. Tampilkan semua postingan

Sabtu, 21 Januari 2017

One of the frequently ask SQL questions in any programming interviews is what is the difference between VARCHAR and CHAR data type in SQL? particularly when your project is using Microsoft SQL Server. You might have seen this couple of times, but given its popularity, nowadays people are asking this question differently e.g. they will ask you how much space a column of VARCHAR(2) data type will take? How many characters can it take? How do you minimize the space? Is it better to use a CHAR variable instead of VARCHAR(2) and why? These are some of the really interesting question and more meaningful than classical SQL questions like the difference between char vs varchar data type question.
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Minggu, 10 April 2016

Oracle and Microsoft SQL Server are two of the most popular database but they are very different with each other and if you are migrating SQL queries or database, tables from Oracle 11g database to Microsoft SQL Server 2008 then you are bound to face some issues. Main reason of these porting issues are features which are supported and exists in Oracle database, but not available in Microsoft SQL Server 2008 like SEQUENCE, Order by clause in subqueries, and derived tables, derived table without name etc. I am sure there are few more and it will surface based upon different database objects you are using in your tables and queries. On another hand SQL engine for SQL Server and Sybase are very much similar, at least syntactically, and if you are migrating queries from SQL Server to Sybase you can do that without much hassle, of course, there will be slight changes but not as much like Oracle.
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Minggu, 03 April 2016

Sometimes, you need the result of SQL SELECT clause as a comma separated String e.g. if you are outputting ids of white-listed products. By default, the SELECT command will print each row in one line and you get a column of names or ids. If you need a comma separated String then you probably need to use a text editor like Notepad++, Edit Plus, or a tool like Microsoft Excel to convert that column of values into a big CSV String. I often use a text editor like edit plus to replace the \n to comma (,) to create such CSV string because it support regular expression based find and replace operation. Suddenly, a thought came to my mind, why not do this in T-SQL in the SQL Server. It would not only save the time but also give you options like create a sorted list of comma separated String using order by clause. It's a nice trick and useful in many scenarios especially if you are working with data drive application.
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Sabtu, 29 Desember 2012

The main difference between Primary key and Foreign key in a table is that it�s the same column which behaves as primary key in the parent table and as a foreign key in a child table. For example in Customer and Order relationship, customer_id is the primary key in Customer table but a foreign key in Order table. By the way, what is a foreign key in a table and difference between Primary and Foreign key are some of the popular SQL interview questions, much like truncate vs delete in SQL or difference between correlated and noncorrelated subquery? We have been learning key SQL concepts along with these frequently asked SQL questions and in this SQL tutorial, we will discuss what is a foreign key in SQL and purpose of the foreign key in any table. By the way, this is the third article related to a primary key in SQL, other being difference between primary and unique key and How to find second highest salary in SQL. If you are preparing for any technical job interview where you expect some SQL questions, check out these questions, they are worth preparing.
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Rabu, 26 Desember 2012

How to add column in existing table with default value is another popular SQL interview question asked for Junior level programming job interviews. Though syntax of SQL query to add column with default value varies little bit from database to database, it always been performed using ALTER keyword of ANSI SQL. Adding column in existing table in MySQL database is rather easy and straight forward and we will see example of SQL query for MySQL database which adds a column with default value. You can also provide constraints like NULL or NOT NULL while adding new column in table. In this SQL tutorial we are adding third column in a table called Contacts which contains name and phone of contacts. Now we want to add another column email with default value "abc@yahoo.com". We will use ALTER command in SQL to do that. By the way this is next in our SQL tutorials e.g. How to join three tables in SQL and SQL query to find duplicate records in table. If you haven't read them yet, then you may find them useful.

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Automatic incremented ID, Sequence or Identity columns are those columns in any table whose value is automatically incremented by database based upon predefined rule. Almost all databases e.g. Microsoft SQL Server, MySQL, Oracleor Sybase supports auto incremented identity columns but in different ways like Oracle provides SEQUENCE object which can be used to generate automatic numbers, Microsoft SQL Server upto 2008 version provides IDENTITY() functions for similar purpose. Sybase also has IDENTITY function but little different than SQL Server and MySQL uses auto_incremented keyword to make any numeric column auto incremented. As first normal form advised about primary keys which is used to uniquely identity row and if there is no natural column or combination of column exists to act as primary key, mostly database developer use auto incremented surrogate keys which is used to uniquely identify each row. In this SQL tutorial we will see how to generate auto incremented ID column in Microsoft SQL Server, Oracle 11g, MySQL and Sybase ASE Server. By the way this SQL article is continuation of my earlier post on SQL and database like difference between truncate and delete in SQL and Finding second highest salary in MySQL and SQL Server. If you haven't got chance to read them than I suggest they are worth looking.
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Selasa, 25 Desember 2012

Some time we need to split a long comma separated String in Stored procedure e.g. Sybase or SQL Server stored procedures. Its quite common to pass comma delimited or delimiter separated String as input parameter to Stored procedure and than later split comma separated String into multiple values inside stored proc. This is not just case of input parameter but you can also have comma separated string in any table data. Unfortunately there is no split() function in Sybase or SQL Server 2005 or 2008 which can directly split string based on delimiter just like in Java string split method. Fortunately Sybase Adaptive Server and Microsoft SQL server has functions like CHARINDEX and PATINDEX which can be used to split comma separated String. This is next on our SQL tutorials after seeing SQL query to find duplicate records in table and How to find 2nd and Nth maximum salary in SQL.
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