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6 min readIn PostgreSQL, you can save temporary session variables by using the SET command. These variables are only available for the duration of the current session and will be automatically reset once the session ends.
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4 min readYou can display the number of "missing" hours in Oracle by using a SQL query that calculates the difference between the total hours in a day and the sum of hours recorded in a table. This can be achieved by using aggregate functions such as SUM and GROUP BY to calculate the total hours recorded for each day, and then subtracting this value from the total number of hours in a day (usually 24). The result will be the number of hours that are "missing" or not recorded in the table.
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3 min readTo create a helper function for queries in PostgreSQL, you can define a new function using the CREATE FUNCTION statement. Inside the function, you can write the custom logic that you want to use for querying the database.You can pass parameters to the function to customize the query based on different conditions. This can make your helper function more versatile and reusable for different scenarios.
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5 min readThe "is" keyword in Oracle procedures is used as a delimiter to separate the parameters and the local variables within the procedure definition. It is not necessary for the functionality of the procedure, but helps in improving the readability and organization of the code. By using "is", developers can clearly distinguish between the parameters that are being passed into the procedure and the variables that are used within the procedure's body.
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4 min readTo remove '\r\n' from a base64 string in Oracle, you can use the REPLACE function to replace it with an empty string. Here is an example query that demonstrates how to do this: SELECT REPLACE(base64_string_column, '\r\n', '') AS cleaned_base64_string FROM your_table_name; In this query, 'base64_string_column' is the column in your table that contains the base64 string that you want to clean.
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3 min readTo update partial value in PostgreSQL, you can use the UPDATE statement with a WHERE clause to specify the condition for which rows to update. You can also use the SET clause to specify the columns and values that you want to update. By using a combination of WHERE and SET clauses, you can update only specific columns or values in a table, leaving the rest of the data unchanged. This allows you to update partial values in PostgreSQL without affecting the entire row.
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6 min readTo convert an outer join select query to a merge in Oracle, you can use the MERGE statement in Oracle to perform a similar operation. The MERGE statement allows you to merge data from a source table to a target table based on a specified condition.To convert the outer join select query to a merge statement, you would need to identify the source and target tables, specify the join condition, and define the actions to be taken when a match is found or not found.
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7 min readIn PostgreSQL, the bit data type is used to store fixed-length binary strings. When mapping a column with type bit(24) in PostgreSQL with Hibernate, you can use the @Type annotation along with the BitStringType class provided by Hibernate.To map a column with type bit(24), you can annotate the corresponding field in your entity class with @Column and @Type(type = "org.hibernate.type.BitStringType").
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5 min readTo count the number of files under a specific directory in Hadoop, you can use the Hadoop command line interface (CLI) or write a MapReduce program.Using the Hadoop CLI, you can run the following command: hadoop fs -count -q /path/to/directory This command will provide you with the count of files, directories, and bytes in the specified directory.Alternatively, you can write a MapReduce program to count the number of files in a directory.
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6 min readOne way to update data only when the data is changed in Oracle is by using a trigger. Triggers in Oracle are special kinds of stored procedures that are automatically executed or fired when certain events occur in a database.To implement this, you can create a trigger that is fired before an update operation on a particular table. Within the trigger, you can compare the old and new values of the data being updated. If the data has changed, then you can perform the update operation.
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4 min readTo read a Hadoop MapFile using Python, you can use the pyarrow library, which provides an interface for reading and writing MapFiles. First, you will need to install the pyarrow library using pip install pyarrow. Then, you can use the pyarrow.mapfile module to read the MapFile using the open function. You can then iterate over the records in the MapFile using the iter method of the MapFileReader object and access the key and value of each record using the key and value attributes.