PostgreSQL 相当于 SQL Server 的 TVP

Question

SQL Server has Table Value Parameters which allows you to pass an array of values as a parameter.

What is the appropiate way to achieve something similar to a PostgreSQL query so I can do something like:

select * from product where id in ($1)

I'm using Npgsql .NET library.

https://www.nuget.org/packages/Npgsql/3.0.5

Answer 1

In PostgreSQL you can use arrays instead of list of IDs like:

... where id = any('{1, 2, 3}'::int[])

or

... where id = any(array[1, 2, 3])

which means that id is one of the array's items.

Read more about arrays operators and functions.

To pass array as a parameter from third party languages you can use at least first variant:

... where id = any($1 ::int[])

where $1 is a string parameter looks like {1, 2, 3} . Note that a space between $1 and ::int[] - it may be necessary for some clients.

Not sure about C# is it supports array parameters directly.

Answer 2

In Postgres you can use IN operator in two ways:

expression IN (value [, ...])
expression IN (subquery)

Read in the documetation: first variant , second variant or this overview .

Answer 3

Here's an example for inserts in C# using Dapper and Npgsql - it inserts 1, 2, 3 into a temporary table and selects them back out ordered descending, so it will print 3 2 1 to the console. The trick here is the Postgres unnest() function, which expands an array to a set of rows:

var results = await conn.QueryAsync<int>(@"
    CREATE TEMPORARY TABLE DapperNpgsqlArrayParameterDemo (id int not null primary key);
    INSERT INTO DapperNpgsqlArrayParameterDemo (id) SELECT unnest(@numbers);
    SELECT id from DapperNpgsqlArrayParameterDemo order by id desc;",
    new { numbers = new int[] { 1, 2, 3 } });
foreach(var item in results)
{
    Console.WriteLine($"found {item}.");
}