Posts (page 69)
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4 min readTo concatenate a new column on a query result in PostgreSQL, you can use the || operator. This operator is used for concatenating strings in PostgreSQL.For example, you can write a query like this:SELECT first_name || ' ' || last_name AS full_name FROM customers;In this query, the || operator is used to concatenate the first_name and last_name columns with a space in between, and the result is aliased as full_name.
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4 min readTo pass the query results to a mod function in PostgreSQL, you can first write your query to retrieve the required data. Then, you can use the result of this query as input to the mod function. Ensure that the datatype of the query result is compatible with the mod function. You can directly pass the query result as an argument to the mod function within your SQL statement. This will allow you to calculate the modulus of the query result using the mod function.
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6 min readTo catch the error raised from a PostgreSQL stored procedure in Java, you can use the standard JDBC error handling mechanisms.When calling a stored procedure from Java using JDBC, you can use a try-catch block to catch any SQLException that is thrown. This SQLException will contain information about the error raised by the stored procedure.
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8 min readTo find duplicate case insensitive records in PostgreSQL, you can use the LOWER function to convert the column values to lowercase before comparing them. This way, you can identify records that are the same regardless of their casing.
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4 min readIn PostgreSQL, you can apply a limit conditionally by using a CASE statement in your query. The CASE statement allows you to define different conditions and return different results based on those conditions.For example, if you only want to limit the number of results if a certain condition is met, you can use a CASE statement to check for that condition. If the condition is met, you can apply the limit using the LIMIT keyword.
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5 min readIn PostgreSQL's EXPLAIN ANALYZE feature, "unique" refers to the use of a unique index to enforce uniqueness in a table. When a query involves accessing a unique index to retrieve data, the "unique" keyword will appear in the EXPLAIN ANALYZE output. This indicates that PostgreSQL is using a unique index to efficiently retrieve and filter the data requested by the query.
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4 min readTo parse serialized JSON in PostgreSQL, you can use the json_populate_record function to convert a JSON object into a record type, json_populate_recordset to convert a JSON array into a set of records, or the jsonb_to_record function to convert a JSONB object into a record type. You can also use the json_extract_path_text function to extract specific values from a JSON object using JSONPath.
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4 min readTo get a specific key from a JSONB column in PostgreSQL, you can use the -> operator followed by the key name you want to extract.For example, if you have a JSONB column named data in a table named json_data, and you want to extract the value of a key named name, you can use the following query: SELECT data->'name' FROM json_data; This will return the value associated with the key name from the JSONB column data in the json_data table.
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5 min readTo execute a PostgreSQL function at a specific time interval, you can use the pg_cron extension, which allows you to schedule jobs directly within the database. This extension integrates cron-like scheduling capabilities into PostgreSQL, making it easy to run functions at predetermined times.First, you need to install the pg_cron extension by running the appropriate SQL script on your database.
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4 min readTo loop through JSON attributes in PostgreSQL, you can use the json_each_text function along with a LATERAL join. This function allows you to unnest a JSON object and return each key-value pair as a separate row. You can then access the key and value attributes in your query to manipulate the data as needed. This can be particularly useful when working with JSON data in PostgreSQL and needing to iterate over the attributes of a JSON object.
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6 min readIn PostgreSQL, you can compare and take non-duplicate text by using the DISTINCT keyword in combination with the SELECT statement. This allows you to retrieve unique values from a column or set of columns in a table.
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7 min readTo insert a comma separated document into PostgreSQL, you will first need to ensure that the table you are inserting the data into has the necessary columns to store the information from the document. You can then use the COPY command in PostgreSQL to load the comma separated document into the table. The COPY command allows you to read data from a file and insert it into a table in bulk.