Posts (page 139)
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7 min readTo get the count of the number of weeks in a month in PostgreSQL, you can use the following query:SELECT COUNT(DISTINCT DATE_TRUNC('week', date_column)) as num_weeks FROM your_table_name WHERE EXTRACT(MONTH FROM date_column) = desired_month_number;Replace "your_table_name" with the name of your actual table and "date_column" with the name of your date column. The "desired_month_number" should be the month you want to calculate the number of weeks for.
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6 min readTo insert CSV data into an Oracle table, you can use the SQL Loader utility provided by Oracle. First, you need to create a control file that specifies the format of the CSV file and the target table. Then, you can use the SQL Loader command to load the data from the CSV file into the Oracle table. Make sure to match the columns in the CSV file with the columns in the Oracle table and define the appropriate data types.
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2 min readTo concatenate string_arr in PostgreSQL, you can use the array_to_string function. This function converts an array to a single string with elements separated by a delimiter of your choice. Simply pass the array you want to concatenate and the delimiter you want to use as arguments to the function. This will give you a concatenated string with the elements of the original array.[rating:e727dd3b-20e7-430f-ba0b-7c16ada6dc22]What is the function for concatenating elements in PostgreSQL.
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4 min readTo execute a multiple value parameter function in Oracle, you need to define the function with parameters that can accept multiple values. These parameters are usually defined as arrays or collections. You can then pass multiple values to these parameters when calling the function.Once the function is defined with multiple value parameters, you can call the function and pass in the values as needed. The function will then process the multiple values and return the desired result.
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6 min readSchema migration for a PostgreSQL database involves making structured changes to the database schema over time without losing any data. To implement schema migration, developers often use tools like Flyway or Liquibase, which allow for versioning of database structures and executing migration scripts.
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5 min readTo delete duplicate rows from a table using a cursor in Oracle, you can follow these steps:Declare a cursor to select the duplicate rows from the table.Use the cursor to fetch each duplicate row one by one.Compare the fetched row with the previous row to determine if it is a duplicate.If the row is a duplicate, delete it from the table.Continue fetching and comparing rows until all duplicate rows have been deleted.
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4 min readIn PostgreSQL, you can extract the weekday from a timestamp using the EXTRACT function along with the DOW or ISODOW specifier. The DOW specifier will return the day of the week with Sunday being 0 and Saturday being 6. The ISODOW specifier will return the day of the week with Monday being 1 and Sunday being 7.
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5 min readTo use PostgreSQL roles to connect to a database, you first need to create a role with the necessary permissions to access the database. This can be done using the CREATE ROLE command in PostgreSQL. Once the role is created, you can then use the \c command in the psql interactive terminal to connect to the database as that role. Alternatively, you can specify the role in the connection string when using a programming language or tool to interact with the database.
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5 min readTo query a JSON array in a JSONB column in PostgreSQL, you can use the jsonb_array_elements function. This function allows you to treat a JSON array as a set of rows that you can query individually. You can use it in combination with other JSON functions to filter, aggregate, or manipulate the data within the array. By using these functions, you can extract specific elements from the JSON array and perform various operations on them within the database.
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3 min readIn PostgreSQL, you can use the following query to know disabled/enabled indexes:SELECT indexname, indexdef::text FROM pg_indexes WHERE tablename = 'your_table_name';In Oracle, you can use the following query to know disabled/enabled indexes:SELECT index_name, status FROM user_indexes WHERE table_name = 'your_table_name';[rating:e727dd3b-20e7-430f-ba0b-7c16ada6dc22]What is the query to identify disabled indexes in Oracle database.
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5 min readTo convert MySQL CONVERT_TZ() function to PostgreSQL, you can use the AT TIME ZONE function in PostgreSQL. The AT TIME ZONE function allows you to convert a timestamp or timestamptz value from one time zone to another. You need to specify the time zone in which the original timestamp is recorded and the time zone to which you want to convert it.
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4 min readTo add results from a JSON stored in PostgreSQL, you can use the JSON functions provided by PostgreSQL. You can extract values from the JSON data and perform operations on them as needed.You can use the json_extract_path_text function to extract values from a JSON column in a table. You can then use these values in your calculations and add them together as required.