Posts (page 7)
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6 min readThere are several strategies that can be implemented to improve the performance of Oracle inserts.One approach is to use bulk insert operations instead of single row inserts. This can be achieved by using the INSERT INTO ... SELECT syntax or by using the FORALL statement in PL/SQL to process multiple rows at once.Another strategy is to minimize the number of indexes on the table being inserted into, as each index adds overhead to the insert operation.
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4 min readTo remove duplicate values of a group in Oracle SQL, you can use the DISTINCT keyword in your query. This keyword eliminates duplicate rows from the result set, so you will only get unique values for the specified group. You can also use the GROUP BY clause to group the results based on a particular column or set of columns, and then apply the DISTINCT keyword to remove any duplicate values within each group.
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5 min readTo create a table based on multiple tables in Oracle, you can use the CREATE TABLE AS statement. This statement allows you to create a new table by selecting data from one or more existing tables. You can specify the columns you want to include in the new table and use queries to extract data from the multiple tables.For example, you can create a new table by combining data from two existing tables using a query like this: CREATE TABLE new_table AS SELECT table1.column1, table1.column2, table2.
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6 min readTo rebuild an index of a specific table in Oracle, you can use the ALTER INDEX statement. First, you need to determine the name of the index that you want to rebuild by querying the DBA_INDEXES or ALL_INDEXES views. Once you have the index name, you can use the ALTER INDEX statement like this:ALTER INDEX index_name REBUILD;This statement will rebuild the specified index on the table. Rebuilding an index can help improve the efficiency of queries and data retrieval operations on the table.
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6 min readTo pass a condition to a PostgreSQL query in a cursor, you can use a variable to store the condition and then use that variable in the WHERE clause of your query. This allows you to dynamically change the condition based on your requirements. You can declare a variable at the beginning of your cursor and then assign the condition to that variable. When you execute the cursor, you can use the variable in the WHERE clause to filter the results based on the condition passed.
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5 min readTo modify an array under a specific JSONB key in PostgreSQL, you can use the jsonb_set function. This function allows you to specify the path to the key you want to modify and update the array under that key.
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4 min readTo filter a PostgreSQL query by date using Python, you can use the psycopg2 library to connect to the database and execute SQL queries. You can specify the date range using the WHERE clause in your query. For example, if you want to filter records that fall within a specific date range, you can use the following syntax: import psycopg2 conn = psycopg2.connect("dbname=mydb user=postgres password=secret") cur = conn.
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3 min readIn PostgreSQL, you can cast a string into an integer by using the CAST function or the :: operator. For example, if you have a string '123' and you want to convert it into an integer, you can do so by using either of the following queries:Using the CAST function: SELECT CAST('123' AS INTEGER); Using the :: operator: SELECT '123'::INTEGER; Both of these queries will convert the string '123' into an integer value of 123.
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3 min readTo join 2 columns and extract year and count in PostreSQL, you can use the following SQL query:SELECT EXTRACT(year FROM date_column) AS year, COUNT(*) AS count FROM your_table GROUP BY year;This query will extract the year from a date column in your table, and then count the occurrences of each unique year. The result will be a list of years and their corresponding count in the table.[rating:fb1c48f9-d45d-4887-9bae-8f42148c208d]What is a common table expression (CTE) in PostgreSQL.
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4 min readTo concatenate two tables in PostgreSQL, you can use the UNION operator. This operator allows you to combine the results of two separate SELECT statements into a single result set. When using UNION, both tables must have the same number of columns and corresponding columns should have compatible data types. Additionally, UNION removes any duplicate rows from the final result set.
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4 min readTo export a JSONB column in PostgreSQL, you can use the jsonb_to_json function to convert the JSONB data into JSON format. Then, you can use the jsonb_pretty function if you want to pretty print the JSON data. Finally, you can use the COPY command to export the JSON data to a file or another location. By combining these functions and commands, you can easily export JSONB data from a PostgreSQL table.
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3 min readIn PostgreSQL, you can convert a bigint value representing a timestamp into a formatted date string using the TO_TIMESTAMP function along with the TO_CHAR function.First, you need to cast the bigint value to a timestamp using the TO_TIMESTAMP function. For example, if your bigint value is stored in a column named "timestamp_column" in a table called "example_table", you can convert it to a timestamp like this:TO_TIMESTAMP(example_table.