Build a SQL Query BuilderStep 5 of 5

A Preset with count_all

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Step 5 - A Preset with count_all

Builders often ship with presets - small helpers that assemble a common query so callers do not repeat the chain. This is the spirit of a Director in the Builder pattern.

Implement the classmethod count_all(table). Using a fresh builder, select the single column COUNT(), set the table with from_, and return the built string. The result must be exactly SELECT COUNT() FROM <table>.

Hints
Starter code
class QueryBuilder:
    def __init__(self):
        self.columns = []
        self.table = None
        self.wheres = []
        self.order = None
        self._limit = None

    def select(self, *cols):
        self.columns = list(cols)
        return self

    def from_(self, table):
        self.table = table
        return self

    def where(self, condition):
        self.wheres.append(condition)
        return self

    def order_by(self, col):
        self.order = col
        return self

    def limit(self, n):
        self._limit = n
        return self

    def reset(self):
        self.columns = []
        self.table = None
        self.wheres = []
        self.order = None
        self._limit = None
        return self

    def build(self):
        cols = ", ".join(self.columns) if self.columns else "*"
        sql = "SELECT " + cols + " FROM " + self.table
        if self.wheres:
            sql += " WHERE " + " AND ".join(self.wheres)
        if self.order is not None:
            sql += " ORDER BY " + self.order
        if self._limit is not None:
            sql += " LIMIT " + str(self._limit)
        return sql

    @classmethod
    def count_all(cls, table):
        """Return a COUNT(*) query for the given table using the builder."""
        # TODO: return cls().select("COUNT(*)").from_(table).build()
        pass
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