http://viralpatel.net/blogs/useful-oracle-queries/
Here’s a list of 40+ Useful Oracle queries that every Oracle developer must bookmark. These queries range from date manipulation,getting server info,get execution status,calculate database size etc.
Quickly returns the first day of current month. Instead of current month you want to find first day of month where a date falls,replace SYSDATE with any date column/value.
This query is similar to above but returns last day of current month. One thing worth noting is that it automatically takes care of leap year. So if you have 29 days in Feb,it will return 29/2. Also similar to above query replace SYSDATE with any other date column/value to find last day of that particular month.
First day of year is always 1-Jan. This query can be use in stored procedure where you quickly want first day of year for some calculation.
Similar to above query. Instead of first day this query returns last day of current year.
Now this is useful. This query returns number of days in current month. You can change SYSDATE with any date/value to know number of days in that month.
Below query calculates number of days left in current month.
Use this query to get difference between two dates in number of days.
Use second query if you need to find number of days since some specific date. In this example number of days since any employee is hired.
This clever query displays start date and end date of each month in current year. You might want to use this for certain types of calculations.
A simple query that can be used to check if a table exists before you create it. This way you can make your create table script rerunnable. Just replace table_name with actual table you want to check. This query will check if table exists for current user (from where the query is executed).
Simple query to check if a particular column exists in table. Useful when you tries to add new column in table using ALTER TABLE statement,you might wanna check if column already exists before adding one.
This query gives you the DDL statement for any table. Notice we have pass ‘TABLE’ as first parameter. This query can be generalized to get DDL statement of any database object. For example to get DDL for a view just replace first argument with ‘VIEW’ and second with your view name and so.
Yet another query to get current schema name.
Yet another query to change the current schema. Useful when your script is expected to run under certain user but is actually executed by other user. It is always safe to set the current user to what your script expects.
Returns the Oracle database version.
Some system default information.
Display the character set information of database.
Now this ones tricky. Sometime you might querying database on some value independent of case. In your query you might do UPPER(..) = UPPER(..) on both sides to make it case insensitive. Now in such cases,you might want to make your index case insensitive so that they don’t occupy more space. Feel free to experiment with this one.
Yet another DDL query to resize table space.
Query to check if autoextend is on or off for a given tablespace.
Query to add datafile in a tablespace.
Yet another query to increase the datafile size of a given datafile.
Gives the actual database size in GB.
Gives the size occupied by data in this database.
Give the size of user in MBs.
This query will display last SQL query fired by each user in this database. Notice how this query display last SQL per each session.
Displays CPU usage for each User. Useful to understand database load by user.
Show the progress of long running queries.
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This is for those who wants to do some voodoo magic using process ids and session ids.
Output:
Below query will search for string ‘FOO_SOMETHING’ in all package source. This query comes handy when you want to find a particular procedure or function call from all the source code.
The query can come quite handy when you have comma separated data string that you need to convert into table so that you can use other SQL queries like IN or NOT IN. Here we are converting ‘AA,BB,CC,DD,EE,FF’ string to table containing AA,CC etc. as each row. Once you have this table you can join it with other table to quickly do some useful stuffs.
This ones straight forward. Use this when your table does not have primary key or you cannot be sure if record having max primary key is the latest one.
You might want to generate some random data to quickly insert in table for testing. Below query help you do that. Read this article for more details. More info:
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Plain old random number generator in Oracle. This ones generate a random number between 0 and 100. Change the multiplier to number that you want to set limit for.
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This one can be written in multiple ways. You can create count(*) on a table to know number of rows. But this query is more efficient given the fact that we are only interested in knowing if table has any data.
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If you have some cool query that can make life of other Oracle developers easy,do share in comment section.
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