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Script Development / SQL Construction DFF.SQL

Using DFF.SQL(...) can conveniently generate dynamic SQL statements, avoiding SQL injection issues caused by manual SQL concatenation.

Parameter Type Required / Default Value Description
sql str Required SQL statement, may include parameter placeholders.
? represents an escaped parameter;
?? represents an unescaped parameter.
sql_params list None SQL parameters

Most SQL-based connectors already have this feature built-in

For most objects created via DFF.CONN(...), which operate on SQL-based connectors, this functionality is already built-in and can be used directly.

You can directly use conn.query(sql, sql_params) without needing to call this method separately.

This method is mainly used for debugging SQL statements, allowing you to observe the actual executed SQL using print(...).

Example
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sql = 'SELECT * FROM ?? WHERE id = ?'
sql_params = [ 'users', 'user-001' ]
print(DFF.SQL(sql, sql_params))
Example Output
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SELECT * FROM users WHERE id = 'user-001'

Parameter Expansion

To facilitate the generation of dynamic SQL, this method will expand parameters based on the type of values in sql_params.

It allows users to package an uncertain number of items as a single parameter, which the system will automatically expand.

When using this, you can fill in arrays or lists for specific parameter placeholders, such as:

Array Expansion

Parameters that are arrays will automatically expand into the following form:

Array Parameter Expansion
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p1, p2, p3, ...
Example 1
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sql = 'SELECT * FROM ?? WHERE status IN (?)'
sql_params = [
    # Corresponds to the first placeholder ??
    'demo',

    # Corresponds to the second placeholder ?, with array value, automatically expands into multiple values
    [ 'error', 'warning' ]
]
result = db.query(sql, sql_params=sql_params)
Actual Executed SQL
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SELECT * FROM demo WHERE status IN ('error', 'warning')

For parameters that are arrays whose elements are also arrays, a two-level expansion will occur in the following form:

Two-Dimensional Array Parameter Expansion
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(p1_1, p1_2, p1_3, ...), (p2_1, p2_2, p2_3, ...), (p3_1, p3_2, p3_3, ...), ...`.
Example 2
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sql = 'INSERT INTO ?? (id, name, value) VALUES ?'
sql_params = [
    # Corresponds to the first placeholder ??
    'demo',

    # Corresponds to the second placeholder ?, with array value, automatically expands into multiple values (i.e., multiple database records)
    [
        # Elements within the array value are still arrays, continuing automatic expansion (i.e., multiple fields per record)
        [ 1, 'zhang3', 100 ],
        [ 1, 'li4', 200 ],
    ]
]
effected_rows = db.non_query(sql, sql_params=sql_params)
Actual Executed SQL
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INSERT INTO demo (id, name, value) VALUES (1, 'zhang3', 100), (1, 'li4', 200)

Dictionary Expansion

Example
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sql = 'INSERT INTO ?? SET ?'
sql_params = [
    # Corresponds to the first placeholder ??
    'demo',

    # Corresponds to the second placeholder ?, dictionary automatically expands into multiple assignment syntaxes
    {
      'id'   : 1,
      'name' : 'zhang3',
      'value': 100,
    }
]
effected_rows = db.non_query(sql, sql_params=sql_params)
Actual Executed SQL
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INSERT INTO demo SET id = 1, name = 'zhang3', value = 100