type2sql

Code generator for Python classes to flattened relational SQL Table types

For generating SQL code, attributes are flattened, that is nested classes, and lists are generated as single SQL columns. A reverse process happens when generating Python code, that is, Python object can be instantiated from flattened SQL columns.

Annotation

Instances of type2sql.Meta class can be used to annotate Python types. Meta class supports the following, all optional, attributes:

• name: SQL column name, when omitted, Python attribute name is used
• size: the size of the SQL column. It can be either a pair of numbers specified as a tuple or a single number
• occurs: relevant when converting python attributes that are defined as list. A list is flattened to create as many instances as specified by this parameter. Note that the name must be specified and must include {n} to give unique names to flattened column names
• skip: if specified, this attribute is skipped when any SQL statements are generated. Other specifications, if specified, are ignored
• default: default value for the generated SQL column.

Supported Python types

Supported Python types:

Usage

Install type2sql as a dependency in other Python applications or modules that contain target classes for code generation. Use the following functions to generate the required code.

• gen_select(<class>[, <table>]) generates SELECT SQL statement
• gen_ddl(<class>[, <table>]) generates CREATE TABLE SQL statement
• gen_load(<class>[, <fn>]) generates a Python function to instantiate Python type that accepts flattened values as parameters

Example

@dataclass
class Address:
     street1: Annotated[str,        Meta(name="ST1_NM",  size=60)]
     street2: Annotated[str | None, Meta(name="ST2_NM",  size=60)]
     city:    Annotated[str,        Meta(name="CITY_NM", size=30)]
     zip:     Annotated[str,        Meta(name="ZIP_CD",  size=9)]


@dataclass
class Customer:
     name: Annotated[str,           Meta(name="CUST_NM", size=60)]
     addr: Annotated[list[Address], Meta(name="ADDR{n}_{sub}", occurs=2)]


print(gen_ddl(Customer, "FIN.CUSTOMER"))

The above script will print:

CREATE TABLE FIN.CUSTOMER (
    CUST_NM        VARCHAR(60) NOT NULL,
    ADDR1_ST1_NM   VARCHAR(60),
    ADDR1_ST2_NM   VARCHAR(60),
    ADDR1_CITY_NM  VARCHAR(30),
    ADDR1_ZIP_CD   VARCHAR(9),
    ADDR2_ST1_NM   VARCHAR(60),
    ADDR2_ST2_NM   VARCHAR(60),
    ADDR2_CITY_NM  VARCHAR(30),
    ADDR2_ZIP_CD   VARCHAR(9)
)

More examples can be found in the test suite under tests/ folder.