docs: Add CLAUDE.md with codebase guidance

Create comprehensive documentation for future Claude Code instances working in this repository, including:
- Development commands for testing, building, and code quality
- Core architecture overview of the SQL query builder system
- Directory structure and component explanations
- Testing patterns and conventions
- Key dependencies and their purposes

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

select_dataset.go

@@ -4,10 +4,10 @@ import (
 	"context"
 	"fmt"
 
-	"git.fsdpf.net/go/db/v2/exec"
-	"git.fsdpf.net/go/db/v2/exp"
-	"git.fsdpf.net/go/db/v2/internal/errors"
-	"git.fsdpf.net/go/db/v2/internal/sb"
+	"git.fsdpf.net/go/db/exec"
+	"git.fsdpf.net/go/db/exp"
+	"git.fsdpf.net/go/db/internal/errors"
+	"git.fsdpf.net/go/db/internal/sb"
 )
 
 // Dataset for creating and/or executing SELECT SQL statements.
@@ -17,6 +17,7 @@ type SelectDataset struct {
 	isPrepared   prepared
 	queryFactory exec.QueryFactory
 	err          error
+	hooks        exec.Hooks
 }
 
 var ErrQueryFactoryNotFoundError = errors.New(
@@ -94,6 +95,7 @@ func (sd *SelectDataset) copy(clauses exp.SelectClauses) *SelectDataset {
 		isPrepared:   sd.isPrepared,
 		queryFactory: sd.queryFactory,
 		err:          sd.err,
+		hooks:        sd.hooks,
 	}
 }
 
@@ -121,6 +123,7 @@ func (sd *SelectDataset) Update() *UpdateDataset {
 		}
 	}
 	u.clauses = c
+	u.hooks = sd.hooks
 	return u
 }
 
@@ -130,13 +133,18 @@ func (sd *SelectDataset) Insert() *InsertDataset {
 	i := newInsertDataset(sd.dialect.Dialect(), sd.queryFactory).
 		Prepared(sd.isPrepared.Bool())
 	if sd.clauses.HasSources() {
-		i = i.Into(sd.GetClauses().From().Columns()[0])
+		if from, ok := sd.GetClauses().From().Columns()[0].(exp.AliasedExpression); ok {
+			i = i.Into(from.Aliased())
+		} else {
+			i = i.Into(from)
+		}
 	}
 	c := i.clauses
 	for _, ce := range sd.clauses.CommonTables() {
 		c = c.CommonTablesAppend(ce)
 	}
 	i.clauses = c
+	i.hooks = sd.hooks
 	return i
 }
 
@@ -164,6 +172,7 @@ func (sd *SelectDataset) Delete() *DeleteDataset {
 		}
 	}
 	d.clauses = c
+	d.hooks = sd.hooks
 	return d
 }
 
@@ -353,6 +362,11 @@ func (sd *SelectDataset) joinTable(join exp.JoinExpression) *SelectDataset {
 	return sd.copy(sd.clauses.JoinsAppend(join))
 }
 
+// Joins this Datasets table with another, prepend
+func (sd *SelectDataset) JoinPrepend(table exp.Expression, condition exp.JoinCondition, joinType exp.JoinType) *SelectDataset {
+	return sd.copy(sd.clauses.JoinsPrepend(exp.NewConditionedJoinExpression(joinType, table, condition)))
+}
+
 // Adds a WHERE clause. See examples.
 func (sd *SelectDataset) Where(expressions ...exp.Expression) *SelectDataset {
 	return sd.copy(sd.clauses.WhereAppend(expressions...))
@@ -387,6 +401,11 @@ func (sd *SelectDataset) withLock(strength exp.LockStrength, option exp.WaitOpti
 	return sd.copy(sd.clauses.SetLock(exp.NewLock(strength, option, of...)))
 }
 
+// Removes the Group BY clause. See examples.
+func (sd *SelectDataset) ClearGroupBy() *SelectDataset {
+	return sd.copy(sd.clauses.ClearGroupBy())
+}
+
 // Adds a GROUP BY clause. See examples.
 func (sd *SelectDataset) GroupBy(groupBy ...interface{}) *SelectDataset {
 	return sd.copy(sd.clauses.SetGroupBy(exp.NewColumnListExpression(groupBy...)))
@@ -551,8 +570,24 @@ func (sd *SelectDataset) ToSQL() (sql string, params []interface{}, err error) {
 //	db.From("test").Select("col").Executor()
 //
 // See Dataset#ToUpdateSQL for arguments
-func (sd *SelectDataset) Executor() exec.QueryExecutor {
-	return sd.queryFactory.FromSQLBuilder(sd.selectSQLBuilder())
+func (sd *SelectDataset) Executor() (executor exec.QueryExecutor) {
+	if sd.hooks != nil {
+		sd.SetError(sd.hooks.Before(sd))
+	}
+	executor = sd.queryFactory.FromSQLBuilder(sd.selectSQLBuilder())
+	if sd.hooks != nil {
+		executor.Hook(func(result interface{}) error {
+			return sd.hooks.After(sd, result)
+		})
+	}
+	return executor
+}
+
+func (sd *SelectDataset) WithHook(hooks exec.Hooks) *SelectDataset {
+	if sd.hooks == nil {
+		sd.hooks = hooks
+	}
+	return sd
 }
 
 // Appends this Dataset's SELECT statement to the SQLBuilder