Interview Questions.

Question 1. How To Install And Run Hsqldb?

Answer :

Download the hsqldb.Zip document from the download web page in your local pc.
Expand the .Zip the usage of any software which can cope with zip documents. The JDK consists of the command line tool jar. Open a command activate, alternate to the directory wherein the file hsqldb.Zip is, and kind: jar -xf hsqldb.Zip
You want a Java Runtime Environment (JRE) or Java Development Kit (JDK) to run HSQLDB.
Browse the documentation protected in the zip package. Start with 'index.Html'.
Question 2. How To Compile Hsqldb?

Answer :

You do not need to. A compiled JAR of HSQLDB is covered inside the down load. This runs beneath Java 8, nine and 10. Java 5 and Java 6 jar downloads also are to be had from the guide page. If you need to re-assemble HSQLDB, you'll need a JDK.

RDBMS Interview Questions
Question three. How To Create A New Database?

Answer :

A new database is created mechanically if it does no longer but exist. Just hook up with the no longer-yet-existing database the usage of the jdbc: hsqldb: document:«database-route» URL (must replace the remaining element with the direction you need) with the consumer ‘sa’ (or every other call) and a password (can be an empty string). You will use this name and password to connect once more.

Question four. How To Start Programming Jdbc / Hsqldb?

Answer :

HSQLDB comes with PDF and HTML documentation, with example application source code which could help programers who are new to JDBC programming.
Basic pattern applications are within the /src/org/hsqldb/sample folder.
Source code of test programs is beneficial examples of how to use distinctive functions of JDBC and SQL. Check the assets inside the /src/org/hsqldb/check folder.
SQL take a look at scripts are within the /run check folder and offer sizable examples of SQL statements.
Question 5. Where To Get More Documentation?

Answer :

HSQLDB has a preferred JDBC interface. HSQLDB specific JDBC documentation is blanketed within the /doc/src folder.
There are also many books to be had on JDBC programming.
HSQLDB is included in hundreds of books on Java programming. Search Google Books for "HSQLDB".
Hyper-V Interview Questions
Question 6. How To Use Hsqldb Inside Eclipse, Etc.

Answer :

To use HSQLDB at design-time in JBuilder, Eclipse, Net Beans or different tools, you commonly require the plug-in for databases that incorporates the improvement environment. You generally want to add a reference to the HSQLDB jar to the surroundings. Also you commonly want to sign up the JDBC driver (that's part of the hsqldb.Jar) with the environment. A committed plugin is already to be had for Eclipse.

Question 7. How To Upgrade From An Old Version To The Current Version?

Answer :

It is suggested that you near model 1.Eight.X databases with the SHUTDOWN command before they're opened with model 2.X. If the database isn't always read-handiest, it is going to be upgraded to the trendy version.
If you use CACHED tables, the techniques within the System Management and Deployment Issues phase of the Guide ought to be followed. A SHUTDOWN COMPACT after the upgrade is suggested.
Note that an upgrade is a one-way technique, so please always preserve a backup of the vintage database.
Active Directory Interview Questions
Question 8. May I Use Hsqldb In A Commercial Product?

Answer :

Yes. HSQLDB is Open Source and unfastened to use in any commercial product as long as the phrases of the Licenses are met. The Licenses of HSQLDB and Hypersonic SQL (on which a few parts of HSQLDB are primarily based) are each primarily based on the brand new BSD License.

Question nine. Does Hsqldb Store All Data In Memory? Doesn't Memory Run Out As A Result?

Answer :

It shops all records in memory most effective if you need to. By default, CREATE TABLE results in a memory desk, as that is the satisfactory type for smaller tables. For large tables, use CREATE CACHED TABLE and modify the cache size to suite your reminiscence use requirements (as little as 8MB or so).

Domain Name System(DNS) Interview Questions
Question 10. How Does Hsqldb Compare To Other Rdbms Engines In Sql Support / Jdbc Support?

Answer :

HSQLDB has very enormous assist for SQL-ninety two, SQL-1999 and SQL-2011. This help almost matches the Advanced stage of the vintage SQL-92 Standard and the Core level of the brand new Standard, plus one hundred fifty non-obligatory capabilities. SQL assist is greater tremendous than all open-supply database products and includes features that are not yet supported in most closed-supply, business merchandise. JDBC guide is comprehensive and extends to all of the functions which are supported with the aid of the center SQL abilties of the engine.

Question eleven. How Does Hsqldb Compare To Other Rdbms Engines In Speed?

Answer :

This is something that you can measure. Overall, with disk tables, HSQLDB is faster, or at the least comparable in speed to the quickest non-java or java open-supply RDBMS engines. In addition, HSQLDB helps rapid, persistent, reminiscence tables in a database which are a lot faster than conventional disk tables.

You can use the performance exams supplied with HSQLDB. One check, JDBCBench.Java is a preferred TPC-B implementation that measures velocity and reliability of multi-threaded get right of entry to. HSQLDB is extraordinarily fast inside the MVCC mode in this take a look at. Another test, TestCacheSize.Java, is a unmarried-threaded test for pace of INSERT, UPDATE, DELETE and SELECT operations with loads of lots of rows. Some comparisons had been published by means of customers in our mailing lists and on the internet.

Any unique SELECT question speed issues can typically be resolved with moderate adjustments to the query or via adding appropriate indexes. See the Guide for details.

DHCP Interview Questions
Question 12. How Solid Is Hsqldb?

Answer :

HSQLDB 2.X comes after model 1.7.2 / 1.7.Three / 1.Eight.Zero / 2.0 and uses the experience won from large SQL compatibility tests and stress exams by way of software providers that use HSQLDB of their products. Persistence in 2.X is an improved and hardened model of the persistence engine of 1.Eight which was in use for over 5 years.

RDBMS Interview Questions
Question 13. How Solid Is Hsqldb When A Machine Crashes?

Answer :

HSQLDB employs a redo log for data restoration. All the changes to the database are contemplated on this log. Extensive user assessments have validated this mechanism to be powerful and fail-safe in most instances. For delivered security, you could back up the database documents while the engine is jogging the usage of the BACKUP DATABASE command.

By default, a FileDescriptor.Sync () call is made every 500 milliseconds at the redo log document. If the system or the Java technique is likely to crash frequently, you could reduce this down to twenty milliseconds for more common sync() calls. You also can specify zero to force a sync () on each devote. This putting may be modified with "SET FILES WRITE DELAY MILLIS m" or the equivalent connection belongings.

With all the relaxation of the database documents, calls to sync () are made in any respect essential points to make certain the files are steady both after a shutdown and after a crash.

Question 14. What About Multi Threading?

Answer :

HSQLDB 2.X is completely multithreaded. Both the core engine and the Server. In the MVCC mode, a couple of threads can write to the identical table at the same time as other threads carry out SELECT queries.

Question 15. What Are The Limitations Of The Database (length Of Columns, Number Of Tables, Rows...)?

Answer :

There is not any imposed drawback. Number of columns, tables, indexes, size of columns and so forth is constrained handiest via the reminiscence. For instance, a person mentioned using a SELECT declaration with forty one LEFT OUTER JOIN clauses on a big database for a information mining software.

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Question 16. My Database Runs Out Of Memory / How Much Memory Does A Database Need?

Answer :

If only memory tables (CREATE TABLE or CREATE MEMORY TABLE) are used then the database is restrained by the reminiscence. A minimum of about a hundred bytes plus the actual data size are required for each row. If you operate CREATE CACHED TABLE, then the scale of the desk isn't restricted with the aid of the memory beyond a certain minimum length. The statistics and indexes of cached tables are saved to disk. With textual content tables, indexes are memory resident but the facts is cached to disk.

Question 17. What Is The Biggest Known Hsqldb Database?

Answer :

The current length restriction of an HSQLDB database is 8 TB for all CACHED tables and 256GB for every TEXT table. In addition, maximum total lob length is 64TB. If you operate large MEMORY tables, memory is handiest constrained via the allotted JVM reminiscence, which may be numerous GB on cutting-edge machines and 64bit operating systems. We have carried out enormous assessments with the ultra-modern variations the usage of the TestCacheSize and other take a look at programs placing hundreds of thousands of rows and resulting in facts files of as much as sixteen GB and larger LOB sizes. Users have pronounced the use of databases with up pinnacle 900 million rows.

Oracle Memory Management Interview Questions
Question 18. After The Program Is Finished, There Are A Lot Statements In The *.Log File. Why?

Answer :

The database was no longer close down well. When you restart the database, the *.Log document can be processed and an automated checkpoint will be completed. No records devoted before the closing sync() (see beneath machine crash above) can be misplaced. To keep away from this, use the SQL command "SHUTDOWN" when your utility has completed with the database.

The statements that make up the database are saved inside the *.Script report (frequently CREATE statements and INSERT statements for reminiscence tables). Only the statistics of cached tables (CREATE CACHED TABLE) is saved in the *.Statistics report. Also all statistics manipulation operations are saved within the *.Log file (generally DELETE/INSERT) for crash healing. When the SHUTDOWN or CHECKPOINT command is issued to a database, then the *.Script report is re-created and turns into up-to-date. The .Log file is deleted. When the database is restarted, all statements of the *.Script file are carried out first and new statements are appended to the .Log record as the database is used. In addition, there are *.Backup and *.Lobs documents.

Hyper-V Interview Questions
Question 19. The Size Of The .Statistics File Grows In Operation Although The Total Row Count For Cached Tables Has Not Gone Up. Why?

Answer :

HSQLDB tracks most effective as much as a fixed variety of the empty spaces left after DELETE or in the course of UPDATE operations. If the delete fee is better than insert rate, or huge quantity of rows are updated in a unmarried query, then a few areas are left empty. Both CHECKPOINT DEFRAG and SHUTDOWN COMPACT commands will eliminate the empty spaces. In model 2.3.0 empty areas are tracked higher and DEFRAG may be carried out robotically, based on a user-described assets.

Question 20. I Need Transaction Isolation Levels Beyond Read-devoted?

Answer :

HSQLDB 2.X helps READ COMMITTED and SERIALIZABLE isolation stages. It supports each lock-based totally and multisession (MVCC) transaction models, and is completely multithreaded in all modes.

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