Can a foreign key be NULL and/or duplicate?
Please clarify two things for me: Can a Foreign key be NULL? Can a Foreign key be duplicate? As fair as I know, … Read more
oracle
Is there a combination of “LIKE” and “IN” in SQL?
In SQL I (sadly) often have to use “LIKE” conditions due to databases that violate nearly every rule of normalization. I can’t change … Read more
How to generate an entity-relationship (ER) diagram using Oracle SQL Developer
I want to use Oracle SQL Developer to generate an ER diagram for my DB tables but I am new to Oracle and … Read more
How to select the nth row in a SQL database table?
I’m interested in learning some (ideally) database agnostic ways of selecting the nth row from a database table. It would also be interesting … Read more
How to create id with AUTO_INCREMENT on Oracle?
It appears that there is no concept of AUTO_INCREMENT in Oracle, up until and including version 11g. How can I create a column … Read more
Fetch the row which has the Max value for a column
Table: UserId, Value, Date. I want to get the UserId, Value for the max(Date) for each UserId. That is, the Value for each … Read more
Get list of all tables in Oracle?
How do I query an Oracle database to display the names of all tables in it? 2 24 SELECT owner, table_name FROM dba_tables … Read more
How do I limit the number of rows returned by an Oracle query after ordering?
Is there a way to make an Oracle query behave like it contains a MySQL limit clause? In MySQL, I can do this: … Read more
What does the following Oracle error mean: invalid column index
If that’s a SQLException thrown by Java, it’s most likely because you are trying to get or set a value from a ResultSet, … Read more
SQLRecoverableException: I/O Exception: Connection reset
This simply means that something in the backend ( DBMS ) decided to stop working due to unavailability of resources etc. It has … Read more