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6 min readIn Rust, you can add generic types to nested structs by using the same syntax as for regular structs. When defining a nested struct, you can specify one or more generic type parameters inside angle brackets after the struct name.For example, suppose you have a struct called Container that contains another struct called Item, and you want both of them to be generic over a type T.
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4 min readTo fetch only the year from a date in a PostgreSQL table, you can use the EXTRACT function. Here is an example query that retrieves the year from a date column called date_column in a table called your_table_name:SELECT EXTRACT(YEAR FROM date_column) AS year FROM your_table_name;This query will return the year values extracted from the date_column in the specified table.
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5 min readTo provide read-only access to all existing databases in PostgreSQL, you need to first connect to the PostgreSQL server as a superuser or a user with the necessary privileges. Once connected, you can create a new role with the desired permissions to access all databases in a read-only mode. This can be done by executing SQL commands like GRANT CONNECT ON DATABASE dbname TO username; and GRANT SELECT ON DATABASE dbname TO username;.
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4 min readTo append to a list in a Python module written in Rust, you first need to create a function in your Rust module that accepts a list as an argument. Within this function, you can use Rust's capabilities to manipulate the list by appending elements to it using the push method. Once the function is implemented in Rust, you can call it from your Python code by importing the Rust module using a Python-Rust bridge such as PyO3.
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3 min readTo create an array column with unnest and join in PostgreSQL, you can use the unnest() function to expand an array into a set of rows, and then join it with another table based on a matching key. This allows you to work with the individual elements of the array as separate rows in a query. By using unnest() in conjunction with a join statement, you can effectively create a virtual table where each row represents an element of the array column.
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3 min readTo set a maximum value for a column in PostgreSQL, you can use the CHECK constraint when creating the table. This constraint allows you to specify a condition that must be met for every row in the table.
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8 min readTo convert a MongoDB Decimal128 value to JSON in Rust, you can use the bson and serde_json crates. First, you will need to parse the Decimal128 value from your MongoDB document using the bson crate. Once you have the Decimal128 value, you can convert it to a JSON value using the serde_json crate.
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4 min readTo create a type using a specified schema in PostgreSQL, you can use the command CREATE TYPE followed by the type name and the schema name. For example:CREATE TYPE schema_name.type_name AS ( attribute1 data_type, attribute2 data_type, ... );This command will create a new type with the specified attributes in the specified schema. Make sure to replace schema_name and type_name with your desired schema and type names, and data_type with the appropriate data types for your attributes.
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7 min readTo copy a PostgreSQL function, you can use the CREATE FUNCTION command followed by the function name, input parameters, and the definition of the function. You can also use pg_get_functiondef to get the definition of an existing function and then modify it as needed to create a new function. Make sure to specify a new name for the copied function to avoid conflicts with existing functions.
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3 min readTo convert a string to a valid JSON in Rust, you can use the serde_json crate. First, you need to add serde_json as a dependency in your Cargo.toml file: [dependencies] serde = "1.0" serde_json = "1.0" Then, you can use the serde_json::from_str function to convert a JSON string to a JSON value.
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7 min readTo update data with a case conditional in PostgreSQL, you can use the CASE statement within the UPDATE query. The CASE statement allows you to perform different actions based on specific conditions.