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ormread

Read mappable objects from database

Since R2023b

    Description

    example

    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.

    obj = ormread(conn,ormClass,RowFilter=rf) specifies a subset of objects to read from the database.

    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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    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 = recieveProduct(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 the table if it already exists 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 meta.class object containing the class name to read from the database. Use meta.class to resolve class name conflicts such as two classes with the same name in different packages.

    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)

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

    Version History

    Introduced in R2023b