### What changes were proposed in this pull request? This PR intends to clean up the SQL documents in `doc/sql-ref*`. Main changes are as follows; - Fixes wrong syntaxes and capitalize sub-titles - Adds some DDL queries in `Examples` so that users can run examples there - Makes query output in `Examples` follows the `Dataset.showString` (right-aligned) format - Adds/Removes spaces, Indents, or blank lines to follow the format below; ``` --- license... --- ### Description Writes what's the syntax is. ### Syntax {% highlight sql %} SELECT... WHERE... // 4 indents after the second line ... {% endhighlight %} ### Parameters <dl> <dt><code><em>Param Name</em></code></dt> <dd> Param Description </dd> ... </dl> ### Examples {% highlight sql %} -- It is better that users are able to execute example queries here. -- So, we prepare test data in the first section if possible. CREATE TABLE t (key STRING, value DOUBLE); INSERT INTO t VALUES ('a', 1.0), ('a', 2.0), ('b', 3.0), ('c', 4.0); -- query output has 2 indents and it follows the `Dataset.showString` -- format (right-aligned). SELECT * FROM t; +---+-----+ |key|value| +---+-----+ | a| 1.0| | a| 2.0| | b| 3.0| | c| 4.0| +---+-----+ -- Query statements after the second line have 4 indents. SELECT key, SUM(value) FROM t GROUP BY key; +---+----------+ |key|sum(value)| +---+----------+ | c| 4.0| | b| 3.0| | a| 3.0| +---+----------+ ... {% endhighlight %} ### Related Statements * [XXX](xxx.html) * ... ``` ### Why are the changes needed? The most changes of this PR are pretty minor, but I think the consistent formats/rules to write documents are important for long-term maintenance in our community ### Does this PR introduce any user-facing change? Yes. ### How was this patch tested? Manually checked. Closes #28151 from maropu/MakeRightAligned. Authored-by: Takeshi Yamamuro <yamamuro@apache.org> Signed-off-by: Sean Owen <srowen@gmail.com>
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layout | title | displayTitle | license |
---|---|---|---|
global | SHOW COLUMNS | SHOW COLUMNS | 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. |
Description
Return the list of columns in a table. If the table does not exist, an exception is thrown.
Syntax
{% highlight sql %} SHOW COLUMNS table_identifier [ database ] {% endhighlight %}
Parameters
table_identifier
-
Specifies the table name of an existing table. The table may be optionally qualified
with a database name.
Syntax:{ IN | FROM } [ database_name . ] table_name
Note: KeywordsIN
andFROM
are interchangeable. database
-
Specifies an optional database name. The table is resolved from this database when it
is specified. Please note that when this parameter is specified then table
name should not be qualified with a different database name.
Syntax:{ IN | FROM } database_name
Note: KeywordsIN
andFROM
are interchangeable.
Examples
{% highlight sql %}
-- Create customer
table in salesdb
database;
USE salesdb;
CREATE TABLE customer(
cust_cd INT,
name VARCHAR(100),
cust_addr STRING);
-- List the columns of customer
table in current database.
SHOW COLUMNS IN customer;
+---------+
| col_name|
+---------+
| cust_cd|
| name|
|cust_addr|
+---------+
-- List the columns of customer
table in salesdb
database.
SHOW COLUMNS IN salesdb.customer;
+---------+
| col_name|
+---------+
| cust_cd|
| name|
|cust_addr|
+---------+
-- List the columns of customer
table in salesdb
database
SHOW COLUMNS IN customer IN salesdb;
+---------+
| col_name|
+---------+
| cust_cd|
| name|
|cust_addr|
+---------+
{% endhighlight %}