"extract(YEAR from '2018-01-09')",
		"extract(month from '2018-01-09')",

		"extract(hour from '2018-01-09')",
		"extract(day from '2018-01-09')",
		"substring('abcd' from 2 for 2)",
		"substring('abcd' from 2)",
		"substring('abcd' , 2 , 2)",

		"substring('abcd' , 22 )",
		"trim('  aab  ')",
		"trim(leading from '  aab  ')",
		"trim(trailing from '  aab  ')",
		"trim(both from '  aab  ')",

		result.combine(e.Substring.Expr.analyze(s))
		switch {
		case e.Substring.From != nil:
			result.combine(e.Substring.From.analyze(s))
			if e.Substring.For != nil {
				result.combine(e.Substring.Expr.analyze(s))
			}
		case e.Substring.Arg2 != nil:
			result.combine(e.Substring.Arg2.analyze(s))
			if e.Substring.Arg3 != nil {
				result.combine(e.Substring.Arg3.analyze(s))
			}
		default:

	CastType string      `parser:" \"AS\" @(\"BOOL\" | \"INT\" | \"INTEGER\" | \"STRING\" | \"FLOAT\" | \"DECIMAL\" | \"NUMERIC\" | \"TIMESTAMP\") \")\" "`
}

// SubstringFunc represents SUBSTRING sql function
type SubstringFunc struct {
	Expr *PrimaryTerm `parser:" \"SUBSTRING\" \"(\" @@ "`
	From *Operand     `parser:" ( \"FROM\" @@ "`
	For  *Operand     `parser:"   (\"FOR\" @@)? \")\" "`
	Arg2 *Operand     `parser:" | \",\" @@ "`

		expected string // expected SHA256
	}{
		{"shastring", "", "shastring"},
		{emptySHA256, "", emptySHA256},
		{"", "", emptySHA256},
		{"", "X-Amz-Credential=random", unsignedPayload},
		{"", "X-Amz-Credential=random&X-Amz-Content-Sha256=" + unsignedPayload, unsignedPayload},
		{"", "X-Amz-Credential=random&X-Amz-Content-Sha256=shastring", "shastring"},
	}

	for i, testCase := range testCases {