adds connect

docs/examples/UserGuide/getting_started.jl

@@ -9,6 +9,20 @@
 
 # Alternatively, `using Tidier` will import TidierDB in the above manner for you, where TidierDB functions and macros will be available as `DB.@mutate()` and so on, and the TidierData equivalent would be `@mutate()`.
 
+# There are two ways to connect to the database.  you can use `connect` without any need to load any additional packages.
+
+# for example
+
+# ```julia
+# Connect to MySQL
+# conn = connect(:mysql; host="localhost", user="root", password="password", db="mydb")
+# versus
+# Connect to DuckDB
+# julia> conn = connect(:duckdb)
+# ```
+
+# Alternatively, you can use the packages outlined below and establish a connection directly through their respective methods.
+
 # The associated databased packages used to set up connections are currently as follows
 
 # - ClickHouse: ClickHouse.jl

src/TidierDB.jl

@@ -22,7 +22,7 @@ import DuckDB: connect as duckdb_connect
  export db_table, set_sql_mode, @arrange, @group_by, @filter, @select, @mutate, @summarize, @summarise, 
  @distinct, @left_join, @right_join, @inner_join, @count, @window_order, @window_frame, @show_query, @collect, @slice_max, 
  @slice_min, @slice_sample, @rename, copy_to, add_interp_parameter!, duckdb_open, duckdb_connect, @semi_join, @full_join, 
- @anti_join
+ @anti_join, connect
 
 include("docstrings.jl")
 include("structs.jl")
@@ -289,4 +289,44 @@ function copy_to(conn, df_or_path::Union{DataFrame, AbstractString}, name::Strin
     end
 end
 
+
+"""
+$docstring_connect
+"""
+function connect(backend::Symbol; kwargs...)
+    if backend == :MySQL || backend == :mysql 
+        # Required parameters by MySQL.jl: host and user
+        host = get(kwargs, :host, "localhost")
+        user = get(kwargs, :user, "")          
+        password = get(kwargs, :password, "")  
+        # Extract other optional parameters
+        db = get(kwargs, :db, nothing)  
+        port = get(kwargs, :port, nothing)     
+        return DBInterface.connect(MySQL.Connection, host, user, password; db=db, port=port)
+    elseif backend == :LibPQ ||  backend == :libpq 
+        # Construct a connection string from kwargs for LibPQ
+        conn_str = join(["$(k)=$(v)" for (k, v) in kwargs], " ")
+        return LibPQ.Connection(conn_str)
+    elseif backend == :MsSQL || backend == :mssql 
+        # Construct a connection string for ODBC if required for MsSQL
+        conn_str = join(["$(k)=$(v)" for (k, v) in kwargs], ";")
+        return ODBC.Connection(conn_str)
+    elseif backend == :Clickhouse || backend == :clickhouse 
+        # Ensure host and port are specified for ClickHouse
+        if haskey(kwargs, :host) && haskey(kwargs, :port)
+            return ClickHouse.connect(kwargs[:host], kwargs[:port]; (k => v for (k, v) in kwargs if k ∉ [:host, :port])...)
+        else
+            throw(ArgumentError("Missing required positional arguments 'host' and 'port' for ClickHouse."))
+        end
+    elseif backend == :SQLite || backend == :lite
+        db_path = get(kwargs, :db, ":memory:") # Default to in-memory database if not specified
+        return SQLite.DB(db_path)
+    elseif backend == :DuckDB || backend == :duckdb
+        mem = DuckDB.open(":memory:")
+        return DuckDB.connect(mem)
+    else
+        throw(ArgumentError("Unsupported backend: $backend"))
+    end
+end
+
 end

src/docstrings.jl

@@ -994,4 +994,39 @@ julia> db = duckdb_connect(mem);
 
 julia> copy_to(db, df, "df_mem");
 ```
+"""
+
+const docstring_connect = 
+"""
+    connect(backend::Symbol; kwargs...)
+
+This function establishes a database connection based on the specified backend and connection parameters.
+
+# Arguments
+- `backend`: A symbol specifying the database backend to connect to. Supported backends are:
+  - `:duckdb`, `:lite`(SQLite), `:mssql`, `mysql`(for MariaDB and MySQL), `:clickhouse`, `:postgres` 
+- `kwargs`: Keyword arguments specifying the connection parameters for the selected backend. The required parameters vary depending on the backend:
+  - MySQL:
+    - `host`: The host name or IP address of the MySQL server. Default is "localhost".
+    - `user`: The username for authentication. Default is an empty string.
+    - `password`: The password for authentication.
+    - `db`: The name of the database to connect to (optional).
+    - `port`: The port number of the MySQL server (optional).
+
+# Returns
+- A database connection object based on the selected backend.
+
+# Examples
+```julia
+# Connect to MySQL
+# conn = connect(:mysql; host="localhost", user="root", password="password", db="mydb")
+# Connect to PostgreSQL using LibPQ
+# conn = connect(:libpq; host="localhost", dbname="mydb", user="postgres", password="password")
+# Connect to ClickHouse
+# conn = connect(:clickhouse; host="localhost", port=9000, database="mydb", user="default", password="")
+# Connect to SQLite
+# conn = connect(:lite)
+# Connect to DuckDB
+julia> conn = connect(:duckdb)
+DuckDB.Connection(":memory:")
 """