mirror of https://github.com/apache/cassandra
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<?xml version='1.0' encoding='utf-8' ?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"/></head><body><h1 id="CassandraQueryLanguageCQLv0.99.1">Cassandra Query Language (CQL) v0.99.1</h1><h2 id="TableofContents">Table of Contents</h2><ol style="list-style: none;"><li><a href="#CassandraQueryLanguageCQLv0.99.1">Cassandra Query Language (CQL) v0.99.1</a><ol style="list-style: none;"><li><a href="#TableofContents">Table of Contents</a></li><li><a href="#USE">USE</a></li><li><a href="#SELECT">SELECT</a><ol style="list-style: none;"><li><a href="#SpecifyingColumns">Specifying Columns</a></li><li><a href="#ColumnFamily">Column Family</a></li><li><a href="#ConsistencyLevel">Consistency Level</a></li><li><a href="#Filteringrows">Filtering rows</a></li><li><a href="#Limits">Limits</a></li></ol></li><li><a href="#UPDATE">UPDATE</a><ol style="list-style: none;"><li><a href="#ColumnFamily2">Column Family</a></li><li><a href="#ConsistencyLevel2">Consistency Level</a></li><li><a href="#SpecifyingColumnsandRow">Specifying Columns and Row</a></li></ol></li><li><a href="#DELETE">DELETE</a><ol style="list-style: none;"><li><a href="#SpecifyingColumns2">Specifying Columns</a></li><li><a href="#ColumnFamily3">Column Family</a></li><li><a href="#ConsistencyLevel3">Consistency Level</a></li><li><a href="#deleterows">Specifying Rows</a></li></ol></li><li><a href="#TRUNCATE">TRUNCATE</a></li><li><a href="#CREATEKEYSPACE">CREATE KEYSPACE</a></li><li><a href="#CommonIdioms">Common Idioms</a><ol style="list-style: none;"><li><a href="#consistency">Specifying Consistency</a></li><li><a href="#terms">Term specification</a><ol style="list-style: none;"><li><a href="#string_literals">String Literals</a></li><li><a href="#Unicode">Unicode</a></li><li><a href="#Integerslongs">Integers / longs</a></li><li><a href="#UUIDs">UUIDs</a></li></ol></li></ol></li></ol></li></ol><h2 id="USE">USE</h2><p><i>Synopsis:</i></p><pre><code>USE <KEYSPACE>;
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</code></pre><p>A <code>USE</code> statement consists of the <code>USE</code> keyword, followed by a valid keyspace name. Its purpose is to assign the per-connection, current working keyspace. All subsequent keyspace-specific actions will be performed in the context of the supplied value.</p><h2 id="SELECT">SELECT</h2><p><i>Synopsis:</i></p><pre><code>SELECT [FIRST N] [REVERSED] <SELECT EXPR> FROM <COLUMN FAMILY> [USING <CONSISTENCY>]
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[WHERE <CLAUSE>] [LIMIT N];
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</code></pre><p>A <code>SELECT</code> is used to read one or more records from a Cassandra column family. It returns a result-set of rows, where each row consists of a key and a collection of columns corresponding to the query.</p><h3 id="SpecifyingColumns">Specifying Columns</h3><pre><code>SELECT [FIRST N] [REVERSED] name1, name2, name3 FROM ...
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SELECT [FIRST N] [REVERSED] name1..nameN FROM ...
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</code></pre><p>The SELECT expression determines which columns will appear in the results and takes the form of either a comma separated list of names, or a range. The range notation consists of a start and end column name separated by two periods (<code>..</code>). The set of columns returned for a range is start and end inclusive.</p><p>The <code>FIRST</code> option accepts an integer argument and can be used to apply a limit to the number of columns returned per row. When this limit is left unset it defaults to 10,000 columns.</p><p>The <code>REVERSED</code> option causes the sort order of the results to be reversed.</p><p>It is worth noting that unlike the projection in a SQL SELECT, there is no guarantee that the results will contain all of the columns specified. This is because Cassandra is schema-less and there are no guarantees that a given column exists.</p><h3 id="ColumnFamily">Column Family</h3><pre><code>SELECT ... FROM <COLUMN FAMILY> ...
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</code></pre><p>The <code>FROM</code> clause is used to specify the Cassandra column family applicable to a <code>SELECT</code> query.</p><h3 id="ConsistencyLevel">Consistency Level</h3><pre><code>SELECT ... [USING <CONSISTENCY>] ...
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</code></pre><p>Following the column family clause is an optional <a href="#consistency">consistency level specification</a>.</p><h3 id="Filteringrows">Filtering rows</h3><pre><code>SELECT ... WHERE KEY = keyname AND name1 = value1
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SELECT ... WHERE KEY >= startkey and KEY =< endkey AND name1 = value1
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</code></pre><p>The WHERE clause provides for filtering the rows that appear in results. The clause can filter on a key name, or range of keys, and in the case of indexed columns, on column values. Key filters are specified using the <code>KEY</code> keyword, a relational operator, (one of <code>=</code>, <code>></code>, <code>>=</code>, <code><</code>, and <code><=</code>), and a term value. When terms appear on both sides of a relational operator it is assumed the filter applies to an indexed column. With column index filters, the term on the left of the operator is the name, the term on the right is the value to filter <i>on</i>.</p><p><i>Note: The greater-than and less-than operators (<code>></code> and <code><</code>) result in key ranges that are inclusive of the terms. There is no supported notion of “strictly” greater-than or less-than; these operators are merely supported as aliases to <code>>=</code> and <code><=</code>.</i> </p><h3 id="Limits">Limits</h3><pre><code>SELECT ... WHERE <CLAUSE> [LIMIT N] ...
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</code></pre><p>Limiting the number of rows returned can be achieved by adding the <code>LIMIT</code> option to a <code>SELECT</code> expression. <code>LIMIT</code> defaults to 10,000 when left unset.</p><h2 id="UPDATE">UPDATE</h2><p><em>Synopsis:</em></p><pre><code>UPDATE <COLUMN FAMILY> [USING CONSISTENCY.<CL>]
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SET name1 = value1, name2 = value2 WHERE KEY = keyname;
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</code></pre><p>An <code>UPDATE</code> is used to write one or more columns to a record in a Cassandra column family. No results are returned.</p><h3 id="ColumnFamily2">Column Family</h3><pre><code>UPDATE <COLUMN FAMILY> ...
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</code></pre><p>Statements begin with the <code>UPDATE</code> keyword followed by a Cassandra column family name.</p><h3 id="ConsistencyLevel2">Consistency Level</h3><pre><code>UPDATE ... [USING <CONSISTENCY>] ...
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</code></pre><p>Following the column family identifier is an optional <a href="#consistency">consistency level specification</a>.</p><h3 id="SpecifyingColumnsandRow">Specifying Columns and Row</h3><pre><code>UPDATE ... SET name1 = value1, name2 = value2 WHERE KEY = keyname;
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</code></pre><p>Rows are created or updated by supplying column names and values in term assignment format. Multiple columns can be set by separating the name/value pairs using commas. Each update statement requires exactly one key to be specified using a WHERE clause and the <code>KEY</code> keyword.</p><p>Additionally, it is also possible to send multiple UPDATES to a node at once using a batch syntax:</p><pre><code>BEGIN BATCH [USING <CONSISTENCY>]
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UPDATE CF1 SET name1 = value1, name2 = value2 WHERE KEY = keyname1;
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UPDATE CF1 SET name3 = value3 WHERE KEY = keyname2;
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UPDATE CF2 SET name4 = value4, name5 = value5 WHERE KEY = keyname3;
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APPLY BATCH
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</code></pre><p>When batching UPDATEs, a single consistency level is used for the entire batch, it appears after the <code>BEGIN BATCH</code> statement, and uses the standard <a href="#consistency">consistency level specification</a>. Batch UPDATEs default to <code>CONSISTENCY.ONE</code> when left unspecified.</p><p><em>NOTE: While there are no isolation guarantees, <code>UPDATE</code> queries are atomic within a give record.</em></p><h2 id="DELETE">DELETE</h2><p><em>Synopsis:</em></p><pre><code>DELETE [COLUMNS] FROM <COLUMN FAMILY> [USING <CONSISTENCY>] WHERE KEY = keyname1
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DELETE [COLUMNS] FROM <COLUMN FAMILY> [USING <CONSISTENCY>] WHERE KEY IN (keyname1, keyname2);
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</code></pre><p>A <code>DELETE</code> is used to perform the removal of one or more columns from one or more rows.</p><h3 id="SpecifyingColumns2">Specifying Columns</h3><pre><code>DELETE [COLUMNS] ...
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</code></pre><p>Following the <code>DELETE</code> keyword is an optional comma-delimited list of column name terms. When no column names are specified, the remove applies to the entire row(s) matched by the <a href="#deleterows">WHERE clause</a></p><h3 id="ColumnFamily3">Column Family</h3><pre><code>DELETE ... FROM <COLUMN FAMILY> ...
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</code></pre><p>The column family name follows the list of column names.</p><h3 id="ConsistencyLevel3">Consistency Level</h3><pre><code>UPDATE ... [USING <CONSISTENCY>] ...
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</code></pre><p>Following the column family identifier is an optional <a href="#consistency">consistency level specification</a>.</p><h3 id="deleterows">Specifying Rows</h3><pre><code>UPDATE ... WHERE KEY = keyname1
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UPDATE ... WHERE KEY IN (keyname1, keyname2)
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</code></pre><p>The <code>WHERE</code> clause is used to determine which row(s) a <code>DELETE</code> applies to. The first form allows the specification of a single keyname using the <code>KEY</code> keyword and the <code>=</code> operator. The second form allows a list of keyname terms to be specified using the <code>IN</code> notation and a parenthesized list of comma-delimited keyname terms.</p><h2 id="TRUNCATE">TRUNCATE</h2><p><em>Synopsis:</em></p><pre><code>TRUNCATE <COLUMN FAMILY>
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</code></pre><p>Accepts a single argument for the column family name, and permanently removes all data from said column family.</p><h2 id="CREATEKEYSPACE">CREATE KEYSPACE</h2><p><em>Synopsis:</em></p><pre><code>CREATE KEYSPACE <NAME> WITH replication_factor = <NUM> AND strategy_class = "<STRATEGY>"
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[AND strategy_options.<OPTION> = <VALUE> [AND strategy_options.<OPTION> = <VALUE>]];
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</code></pre><p>The <code>CREATE KEYSPACE</code> statement creates a new top-level namespace (aka “keyspace”). Valid names are any string constructed of alphanumeric characters and underscores, but must begin with a letter. Properties such as replication strategy and count are specified during creation using the following accepted keyword arguments:</p><table><tr><th>keyword</th><th>required</th><th>description</th></tr><tr><td>replication_factor</td><td>yes</td><td>Numeric argument that specifies the number of replicas for this keyspace.</td></tr><tr><td>strategy_class</td><td>yes</td><td>Class name to use for managing replica placement. Any of the shipped strategies can be used by specifying the class name relative to org.apache.cassandra.locator, others will need to be fully-qualified and located on the classpath.</td></tr><tr><td>strategy_options</td><td>no</td><td>Some strategies require additional arguments which can be supplied by appending the option name to the <code>strategy_options</code> keyword, separated by a colon (<code>:</code>). For example, a strategy option of “DC1” with a value of “1” would be specified as <code>strategy_options:DC1 = "1"</code>.</td></tr></table><h2 id="CommonIdioms">Common Idioms</h2><h3 id="consistency">Specifying Consistency</h3><pre><code>... USING <CONSISTENCY> ...
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</code></pre><p>Consistency level specifications are made up the keyword <code>USING</code>, followed by a consistency level identifier. Valid consistency levels are as follows:</p><ul><li><code>CONSISTENCY.ZERO</code></li><li><code>CONSISTENCY.ONE</code> (default)</li><li><code>CONSISTENCY.QUORUM</code></li><li><code>CONSISTENCY.ALL</code></li><li><code>CONSISTENCY.DCQUORUM</code></li><li><code>CONSISTENCY.DCQUORUMSYNC</code></li></ul><h3 id="terms">Term specification</h3><p>Where possible, the type of terms are inferred; the following term types are supported:</p><h4 id="string_literals">String Literals</h4><p>String literals are any value enclosed in double-quotes, (`"`). String literals are treated as raw bytes; no interpolation is performed.</p><h4 id="Unicode">Unicode</h4><p>Unicode terms are any double-quoted string prefixed with a lower-case <code>u</code>, for example <code>u"© 2011 The Apache Software Foundation"</code>. Unicode terms are identical to standard <a href="#string_literals">string literals</a>, with the exception that they are encoded to bytes using the UTF-8 charset.</p><h4 id="Integerslongs">Integers / longs</h4><p>Integers are any term consisting soley of unquoted numericals, longs are any otherwise valid integer term followed by an upper case “L”, (e.g. 100L). It is an error to specify an integer term that will not fit in 4 bytes unsigned, or a long that will not fit in 8 bytes unsigned.</p><h4 id="UUIDs">UUIDs</h4><p>There are two types of UUIDs supported by the CQL specification, time-based (version 1) and randomly generated (version 4). These are specified in statements using the <code>timeuuid(<UUID STRING>)</code> and <code>uuid(<UUID STRING>)</code> notations respectively.</p><p>In addition to the hex-based string representation, <code>timeuuid()</code> terms also accept arguments to specify the data-time component. The full list of <code>timeuuid()</code> arguments are:</p><table><tr><th>argument</th><th>example</th><th>behavior</th></tr><tr><td>none</td><td>timeuuid()</td><td>Results in the creation of a new UUID based on system time of the node parsing the query.</td></tr><tr><td>now</td><td>timeuuid(“now”)</td><td>Results in the creation of a new UUID based on system time of the node parsing the query.</td></tr><tr><td>milliseconds since epoch</td><td>timeuuid(1296755320376)</td><td>Creates a UUID with a time component that is based on the supplied time-stamp.</td></tr><tr><td><a href="http://en.wikipedia.org/wiki/8601">iso8601 timestamp</a></td><td>timeuuid(“2011-02-01T14:00-0600”)</td><td>Creates a UUID with a time component that is based on the supplied time-stamp.</td></tr><tr><td><a href="http://tools.ietf.org/html/rfc4122">string representation (hex)</a></td><td>timeuuid(“e9229b24-2fbe-11e0-a4de-0026c650d722”)</td><td>Reproduces the specified version 1 UUID node-side.</td></tr></table></body></html> |