1.1.1

ExplanationExpression type
You must qualify the column-Name by the table name or correlation
name if it is ambiguous.
The qualifier of a column-Name must be the correlation name, if a
correlation name is given to a table that is in a FROM CLAUSE.
The table name is no longer visible as a column-Name qualifier once
it has been aliased by a correlation name.
Allowed in SelectExpression, UPDATE statements, and the WHERE
clauses of data manipulation statements.
Most built-in data types typically have constants associated with
them (as shown in Data types).
Constant
NULL is an untyped constant representing the unknown value.
NULL
Allowed in CAST expressions or in INSERT VALUES lists and
UPDATE SET clauses. Using it in a CAST expression gives it a
specific data type.
A dynamic parameter is a parameter to an SQL statement for which
the value is not specified when the statement is created. Instead, the
Dynamic parameter
statement has a question mark (?) as a placeholder for each dynamic
parameter. See Dynamic parameters .
Dynamic parameters are permitted only in prepared statements. You
must specify values for them before the prepared statement is
executed. The values specified must match the types expected.
Allowed anywhere in an expression where the data type can be easily
deduced. See Dynamic parameters.
Lets you specify the type of NULL or of a dynamic parameter or
convert a value to another type. See CAST function.
CAST expression
Subquery that returns a single row with a single column. See
ScalarSubquery
Scalar subquery
Subquery that returns more than one column and more than one row.
See TableSubquery.
Table subquery
Allowed as a tableExpression in a FROM clause and with EXISTS,
IN, and quantified comparisons.
A conditional expression chooses an expression to evaluate based
on a boolean test.
Conditional expression
Boolean expressions
Boolean expressions are expressions that result in boolean values. Most general expressions can result in boolean
values. Boolean expressions commonly used in a WHERE clause are made of operands operated on by SQL
operators. See SQL Boolean Operators.
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SQL Language Reference