TopMiniSite
-
8 min readConverting PostgreSQL code to Oracle SQL involves making certain syntax adjustments since the two database systems have different SQL dialects. Some key differences to keep in mind include:Oracle SQL uses "dual" table for selecting literal values without a table, whereas PostgreSQL uses "SELECT" with "FROM" clause. Oracle SQL uses "||" for string concatenation, whereas PostgreSQL uses "CONCAT".
-
5 min readTo pass parameters to a custom function in Hibernate, you can use the setParameter method of the Query interface. This method allows you to set parameters for your custom function by specifying the parameter name and value. You can then use these parameters within your custom function logic to perform operations such as filtering, grouping, or ordering data in your query results.
-
5 min readTo change a number column to a date in Oracle, you can use the TO_DATE function to convert the number to a date format. You need to specify the number format and the date format in the function.
-
5 min readIn Hibernate, the mapping between a database table and a persistence class is defined using XML mapping files or annotations. Each persistent class in Hibernate corresponds to a table in the database, and each property in the class corresponds to a column in the table.To find the class-table mapping for a particular entity in Hibernate, you can look at the mapping file (usually in the form of an XML file) or the annotations used in the entity class.
-
3 min readTo replace a string using REGEXP_REPLACE in Oracle, you need to specify the input string, the regular expression pattern to match, the replacement string, and any optional flags for the regex operation.
-
7 min readTo get an Oracle connection from a Hibernate connection, you can first obtain the Hibernate Session object using the sessionFactory.getCurrentSession() method. Once you have the Session object, you can access the underlying JDBC Connection object by calling session.connection(). This will give you a raw JDBC Connection that you can then cast to an Oracle Connection using a typecast.
-
2 min readTo remove all characters except 'e' in Oracle, you can use the REGEXP_REPLACE function. Here is an example query: SELECT REGEXP_REPLACE('Hello world!', '[^e]', '') AS result FROM dual; In this query, the REGEXP_REPLACE function is used to replace all characters that are not 'e' with an empty string. The '[^e]' pattern matches any character except 'e'. So, when you run this query, the result will be 'e'.
-
6 min readTo use an Oracle sequence in Hibernate, you first need to define the sequence in your Oracle database. Once the sequence is created, you can map it to a Hibernate entity by using the @SequenceGenerator annotation on the entity's id field.You need to specify the name of the sequence, the allocation size (the number of sequence values that will be pre-allocated and stored in memory), and the catalog and schema of the sequence if necessary.
-
5 min readTo insert data from multiple tables into one table in Oracle, you can use the INSERT INTO statement along with a SELECT statement that retrieves data from the multiple tables. You can use joins to link the tables and retrieve the data you want to insert into the target table. Make sure that the columns in the target table match the data types of the columns selected from the source tables.
-
4 min readTo write a join query using Hibernate Criteria, you can use the createCriteria method to create a criteria object for each entity you want to join. Then, you can add restrictions and conditions to the criteria objects to specify the join conditions. Finally, you can use the createAlias method to create an alias for the joined entity and specify the join type. This will allow you to perform a join query using Hibernate Criteria.
-
4 min readThe ALTER command is used when killing a session in Oracle because it allows for more control over the termination process. By using the ALTER command, you can explicitly tell Oracle how you want to end the session, whether you want to roll back any uncommitted transactions, or simply kill the session immediately. This helps prevent unexpected behavior and ensures that the session is terminated in a safe and controlled manner.