In Oracle database, the following error message may appear when an incorrect SQL statement is used, in SQL Plus or in anywhere that send SQL queries to the databases such as stored procedure or external programs.

PL/SQL: SQL Statement ignored
PL/SQL: ORA-00947: not enough values

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When database system administrator installs Microsoft SQL Server 2005 and creates a few database engine instances, there will be problem and hard time to remove and uninstall these multiple database instance components and the corresponding SQL Server services. When users try to uninstall Microsoft SQL Server 2005 or remove database instance components using Add and Remove Programs or Uninstall or change a programs (Vista) in Control Panel, only one SQL Server 2005 database engine can be selected. After uninstallation has completed, when users attempt to run the SQL Server 2K5 Uninstall to completely clean remove any other instances or components, the action will fail with error message saying the uninstaller shortcut entry is invalid and asked if you want to remove the link.

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MySQL database server generates binary log files for every transaction to the databases, provided administrator does not disable or comment out the “log-bin” parameter in my.cny configuration file. The binary log files are written in binary format. Although the binary logs, or also known as logbin are mainly used for MySQL database replication purpose, sometimes you may need to examine or read the contents of binary logs in text format, where the mysqlbinlog utility will come in handy.

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MySQL is a very popular free yet powerful database system. But even in great databases, the tables may get fragmented with overhead due to continuous update, or delete and insert operation on data stored in database. Beside, it’s also possibility that the databases may get corrupted. Thus, performing health check on database and optimize MySQL server regularly is an important task.

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Oracle database does not provide an easy user interface to rename a datafile of tablespace, nor database administrator can easily move or relocate the datafile to another location or directory that different from original location on creation of database. The rename or move place task has to be performed via Oracle SQLPlus command line interface. However, if the operation is performed when the tablespace which owns the datefile is online, error will occur.

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Accident may happens, even though it’s costly one. This is especially the case in Oracle database, which stores the database objects physically in data files on hard disk. Fast hand administrators may accidentally delete some of the datafiles, or the datafiles may get corrupted or unreadable on hard disk failure. You may get also some missing datafiles after database recovery process. In any case, missing a or a few datafiles will cause Oracle database to fail to startup, rendering the whole DB inaccessible.

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Oracle RDBMS databases stores data logically in the form of tablespaces and physically in the form of data files. The datafiles are added to the tablespaces as database space requirement grows bigger. However, there are several reasons you may want to remove or delete data files from a tablespace. Such as accidentally add a wrongly sized or unwanted datafile to a tablespace, or the data space usage has became smaller and some data files want to be removed, or attempt to recover Oracle database which fails to start due to missing or corrupted datafiles by removing them, Oracle does not provide an easy way or user interface to delete or drop datafiles from a tablespace. Once a datafile is made part of a tablespace, it can no longer be detached or removed from the tablespace, albeit there are several workarounds.

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phpMyAdmin can be used to export or backup MySQL databases easily. However, if the database size is very big, it probably won’t be a good idea. phpMyAdmin allows users to save database dump as file or display on screen, which involves exporting SQL statements from the server, and transmitting the data across slower network connection or Internet to user’s computer. This process slow the exporting process, increase database locking time and thus MySQL unavailability, slow the server and may simply crash the Apache HTTPD server if too many incoming web connections hogging the system’s resources.

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