[SPARK-31465][SQL][DOCS] Document Literal in SQL Reference

docs/_data/menu-sql.yaml

@@ -78,6 +78,8 @@
   subitems:
     - text: Data Types
       url: sql-ref-datatypes.html
+    - text: Literals
+      url: sql-ref-literals.html
     - text: Null Semantics
       url: sql-ref-null-semantics.html
     - text: NaN Semantics

docs/sql-ref-literals.md

@@ -0,0 +1,155 @@
+---
+layout: global
+title: Literals
+displayTitle: Literals
+license: |
+  Licensed to the Apache Software Foundation (ASF) under one or more
+  contributor license agreements.  See the NOTICE file distributed with
+  this work for additional information regarding copyright ownership.
+  The ASF licenses this file to You under the Apache License, Version 2.0
+  (the "License"); you may not use this file except in compliance with
+  the License.  You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+---
+
+A literal (aka constant) represents a fixed data value. Spark SQL supports the following literals:
+
+ * String Literals
+ * Boolean Literals
+ * Numeric Literals
+ * Datetime Literals
+ * Interval Literals
+
+### String Literals
+
+A string literal is used to specify a character string value.
+<dl>
+  <dt><code><em>Format:</em></code></dt>
+  <dd>
+    <code>'c [ ... ]'</code><br>
+    c: one character of user's character set.
+  </dd>
+</dl>
+<dl>
+  <dt><code><em>Examples:</em></code></dt>
+  <dd>
+    <code>'Hello, World!',   'Spark SQL',   'dbname.schema'</code>
+  </dd>
+</dl>
+
+### Boolean Literals
+
+A boolean literal is used to specify a boolean value.
+<dl>
+  <dt><code><em>Format:</em></code></dt>
+  <dd>
+    <code>TRUE | FALSE </code>
+  </dd>
+</dl>
+
+### Numeric Literals
+
+A numeric literal is used to specify a fixed or floating-point number.
+
+#### Integer Literals
+
+<dl>
+  <dt><code><em>Format:</em></code></dt>
+  <dd>
+    <code>[ + | - ] digit [ ... ] [ l | L ]</code><br>
+    digit: one of 0, 1, 2, 3, 4, 5, 6, 7, 8 or 9 <br>
+    l or L: indicates <code>LongType</code>.
+  </dd>
+</dl>
+<dl>
+  <dt><code><em>Examples:</em></code></dt>
+  <dd>
+    <code>6,  +188,  -54, 1000L</code>
+  </dd>
+</dl>
+
+#### Floating Point and Decimal Literals
+
+<dl>
+  <dt><code><em>Format:</em></code></dt>
+  <dd>
+    <code>
+      [ + | - ] { digit [ ... ] [ . ] [ digit [ ... ] ] | . digit [ ... ] } <br>
+      [ { e | E } [ + | - ] digit [ ... ] ] [ d | D ]
+    </code><br>
+    digit: one of 0, 1, 2, 3, 4, 5, 6, 7, 8 or 9. <br>
+    e or E: indicates that the number is in scientific notation format. <br>
+    d or D: indicates <code>DoubleType</code>
+  </dd>
+</dl>
+<dl>
+  <dt><code><em>Examples:</em></code></dt>
+  <dd>
+    <code>5E2,   3.e6,   2.3E-2,   +3.e+3,   -4D,   0.25</code>
+  </dd>
+</dl>
+
+### Datetime Literals
+
+A Datetime literal is used to specify a datetime data type value.
+
+#### Date Literals
+
+<dl>
+  <dt><code><em>Format:</em></code></dt>
+  <dd>
+    <code>
+      DATE 'YYYY-MM-DD'
+    </code>
+  </dd>
+</dl>
+<dl>
+  <dt><code><em>Examples:</em></code></dt>
+  <dd>
+    <code>DATE '2011-11-11'</code>
+  </dd>
+</dl>
+
+#### Timestamp Literals
+
+<dl>
+  <dt><code><em>Format:</em></code></dt>
+  <dd>
+    <code>
+      TIMESTAMP yyyy-MM-dd HH:mm[:ss.SSSSSSzzz]
+    </code>
+  </dd>
+</dl>
+<dl>
+  <dt><code><em>Examples:</em></code></dt>
+  <dd>
+    <code>TIMESTAMP '1997-01-31 09:26:56.123'</code><br>
+    <code>TIMESTAMP '1997-01-31 09:26:56.66666666CST'</code>
+  </dd>
+</dl>
+
+### Interval Literals
+
+An inerval literal is used to specify a fixed period of time.
+<dl>
+  <dt><code><em>Format:</em></code></dt>
+  <dd>
+    <code>
+      INTERVAL value { YEAR | MONTH | DAY | HOUR | MINUTE | SECOND | MILLISECOND | MICROSECOND }
+    </code>
+  </dd>
+</dl>
+<dl>
+  <dt><code><em>Examples:</em></code></dt>
+  <dd>
+    <code>INTERVAL 3 YEAR</code><br>
+    <code>INTERVAL 3 YEAR 3 HOUR</code>
+  </dd>
+</dl>