ormread

Read mappable objects from database

Since R2023b

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    Syntax

    obj = ormread(conn,ormClass)
    obj = ormread(conn,ormClass,Name=Value)
    obj = ormread(conn,ormObject)

    Description

    obj = ormread(conn,ormClass) reads one or more mappable objects from a database connection of a given class and returns a vector of mappable objects. For more information on mappable objects, see database.orm.mixin.Mappable.

    example

    obj = ormread(conn,ormClass,Name=Value) specifies one or more name-value arguments. For example, set Depth=1 to read in the ForeignKey or LinkTable properties from a class.

    obj = ormread(conn,ormObject) returns an array of objects containing the most recent property values from the database, where ormObject specifies a vector of objects to refresh.

    Examples

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    Open Live Script

    This example depends on the Product class that maps to a database table. This class contains several properties that map to the database, as well as some methods that alter those properties. 

    classdef (TableName = "products") Product < database.orm.mixin.Mappable

    properties(PrimaryKey,ColumnName = "ProductNumber")
        ID int32
    end
    
    properties
        Name string
        Description string
        Quantity int32
    end

    properties(ColumnName = "UnitCost")
        CostPerItem double
    end

    properties(ColumnName = "Manufacturer")
        Supplier string
    end

    properties(ColumnType = "date")
        InventoryDate datetime
    end

    methods
        function obj = Product(id,name,description,supplier,cost,quantity,inventoryDate)
            if nargin ~= 0
                inputElements = numel(id);
                if numel(name) ~= inputElements || ...
                        numel(description) ~= inputElements || ...
                        numel(supplier) ~= inputElements || ...
                        numel(cost) ~= inputElements || ...
                        numel(quantity) ~= inputElements || ...
                        numel(inventoryDate) ~= inputElements
                    error('All inputs must have the same number of elements')
                end
    
                % Preallocate by creating the last object first
                obj(inputElements).ID = id(inputElements);
                obj(inputElements).Name = name(inputElements);
                obj(inputElements).Description = description(inputElements);
                obj(inputElements).Supplier = supplier(inputElements);
                obj(inputElements).CostPerItem = cost(inputElements);
                obj(inputElements).Quantity = quantity(inputElements);
                obj(inputElements).InventoryDate = inventoryDate(inputElements);

                for n = 1:inputElements-1
                    % Fill in the rest of the objects
                    obj(n).ID = id(n);
                    obj(n).Name = name(n);
                    obj(n).Description = description(n);
                    obj(n).Supplier = supplier(n);
                    obj(n).CostPerItem = cost(n);
                    obj(n).Quantity = quantity(n);
                    obj(n).InventoryDate = inventoryDate(n);
                end
            end
        end
        function obj = adjustPrice(obj,amount)
            arguments
                obj (1,1) Product
                amount (1,1) {mustBeNumeric}
            end
           obj.CostPerItem = obj.CostPerItem + amount; 
        end

        function obj = shipProduct(obj,amount)
            arguments
                obj (1,1) Product
                amount (1,1) {mustBePositive,mustBeInteger}
            end

            obj.Quantity = obj.Quantity - amount;
        end

        function obj = receiveProduct(obj,amount)
            arguments
                obj (1,1) Product
                amount (1,1) {mustBePositive,mustBeInteger}
            end

            obj.Quantity = obj.Quantity + amount;
            obj.InventoryDate = datetime('today');
        end

    end

end

    First, create an sqlite database file that does not require a connection to a live database. 

    filename = "orm_demo.db";
if exist(filename,"file")
    conn = sqlite(filename);
else
    conn = sqlite(filename,"create");
end

% Remove it to maintain consistency
execute(conn,"DROP TABLE IF EXISTS products");

    Use the orm2sql function to display the database column information based on the class defined in Product.m. 

    orm2sql(conn,"Product")
    ans = 
    "CREATE TABLE products
     (ProductNumber double, 
     Name text, 
     Description text, 
     Quantity double, 
     UnitCost double, 
     Manufacturer text, 
     InventoryDate date, 
     PRIMARY KEY (ProductNumber))"

    Create a Product object to create and populate a table.

    toy = Product(1,"Toy1","Descr1","CompanyA",24.99,0,datetime(2023,1,1))
    toy = 
  Product with properties:

               ID: 1
             Name: "Toy1"
      Description: "Descr1"
         Quantity: 0
      CostPerItem: 24.9900
         Supplier: "CompanyA"
    InventoryDate: 01-Jan-2023

    Use the ormwrite function to populate the database with the data from toy.

    ormwrite(conn,toy);

    Use the ormread method to read data from the database. This method uses the mapping to determine which tables to read, and also determines how the column values correspond to the properties.

    clear toy 
ormread(conn,"Product")
    ans = 
  Product with properties:

               ID: 1
             Name: "Toy1"
      Description: "Descr1"
         Quantity: 0
      CostPerItem: 24.9900
         Supplier: "CompanyA"
    InventoryDate: 01-Jan-2023


    clear ans
close(conn)

    Input Arguments

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    Database connection, specified as a scalar database.relational.connection object.

    Class identity, specified as a character vector, string scalar, or scalar matlab.metadata.Class object containing the class name to read from the database. Use matlab.metadata.Class to resolve class name conflicts such as two classes with the same name in different packages.

    Mappable object to refresh, specified as a vector. For more information on mappable objects, see database.orm.mixin.Mappable.

    Name-Value Arguments

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    Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

    Example: obj = ormread(conn,ormClass,Depth=1)

    Row filter condition, specified as a scalar or vector of matlab.io.RowFilter objects returned from the rowfilter function.

    Example: rf = rowfilter("productnumber"); rf = rf.productnumber <= 5; ormread(conn,tablename,RowFilter=rf)

    Class depth, specified as a nonnegative scalar integer. Use Depth to choose a subset of the ForeignKey or LinkTable property in the class hierarchy to read before stopping. By default, ormread reads all properties in the hierarchy including nested ones. For example, you can set

    • Depth=0 to read in information about the input class without reading any ForeignKey or LinkTable properties.

    • Depth=1 to read in ForeignKey or LinkTable properties of the input class, while ignoring any nested ForeignKey or LinkTable properties.

    • Depth=2 to read in ForeignKey or LinkTable properties of the input class and one level of nested ForeignKey or LinkTable properties.

    Example: obj = ormread(conn,ormClass,Depth=1)

    Version History

    Introduced in R2023b

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    See Also

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