apache-ignite
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15
16= Data Definition Language (DDL)
17
18:toclevels:
19
20This page encompasses all data definition language (DDL) commands supported by Ignite.
21
22== CREATE TABLE
23
24The command creates a new Ignite cache and defines a SQL table on top of it. The underlying cache stores the data in
25the form of key-value pairs while the table allows processing the data with SQL queries.
26
27The table will reside in the link:SQL/schemas[Schema] specified in the connection parameters. If no schema is specified,
28the `PUBLIC` will be used as a default.
29
30The `CREATE TABLE` command is synchronous. Moreover, it blocks the execution of other DDL commands that are issued before the
31`CREATE TABLE` command has finished execution. The execution of DML commands is not affected and can be performed in parallel.
32
33[source,sql]
34----
35CREATE TABLE [IF NOT EXISTS] tableName (tableColumn [, tableColumn]...
36[, PRIMARY KEY (columnName [,columnName]...)])
37[WITH "paramName=paramValue [,paramName=paramValue]..."]
38
39tableColumn := columnName columnType [DEFAULT defaultValue] [PRIMARY KEY]
40----
41
42
43Parameters:
44
45* `tableName` - name of the table.
46* `tableColumn` - name and type of a column to be created in the new table.
47* `columnName` - name of a previously defined column.
48* `DEFAULT` - specifies a default value for the column. Only constant values are accepted.
49* `IF NOT EXISTS` - create the table only if a table with the same name does not exist.
50* `PRIMARY KEY` - specifies a primary key for the table that can consist of a single column or multiple columns.
51* `WITH` - accepts additional parameters not defined by ANSI-99 SQL:
52
53** `TEMPLATE=<cache's template name>` - case-sensitive name of a link:configuring-caches/configuration-overview#cache-templates[cache template]. A template is an instance of the `CacheConfiguration` class registered by calling `Ignite.addCacheConfiguration()`. Use predefined `TEMPLATE=PARTITIONED` or `TEMPLATE=REPLICATED` templates to create the cache with the corresponding replication mode. The rest of the parameters will be those that are defined in the `CacheConfiguration` object. By default, `TEMPLATE=PARTITIONED` is used if the template is not specified explicitly.
54** `BACKUPS=<number of backups>` - sets the number of link:configuring-caches/configuring-backups[partition backups]. If neither this nor the `TEMPLATE` parameter is set, then the cache is created with `0` backup copies.
55** `ATOMICITY=<ATOMIC | TRANSACTIONAL>` - sets link:key-value-api/transactions[atomicity mode] for the underlying cache. If neither this nor the `TEMPLATE` parameter is set, then the cache is created with the `ATOMIC` mode enabled.
56** `WRITE_SYNCHRONIZATION_MODE=<PRIMARY_SYNC | FULL_SYNC | FULL_ASYNC>` -
57sets the write synchronization mode for the underlying cache. If neither this nor the `TEMPLATE` parameter is set, then the cache is created with `FULL_SYNC` mode enabled.
58** `CACHE_GROUP=<group name>` - specifies the link:configuring-caches/cache-groups[group name] the underlying cache belongs to.
59** `AFFINITY_KEY=<affinity key column name>` - specifies an link:data-modeling/affinity-collocation[affinity key] name which is a column of the `PRIMARY KEY` constraint.
60** `CACHE_NAME=<custom name of the new cache>` - the name of the underlying cache created by the command,
61or the `SQL_{SCHEMA_NAME}_{TABLE}` format will be used if the parameter not specified.
62** `DATA_REGION=<existing data region name>` - name of the link:memory-configuration/data-regions[data region] where table entries should be stored. By default, Ignite stores all the data in a default region.
63** `PARALLELISM=<number of SQL execution threads>` - SQL queries are executed by a single thread on each node by default, but certain scenarios can benefit from multi-threaded execution, see link:perf-and-troubleshooting/sql-tuning#query-parallelism[Query Parallelism] for details.
64** `KEY_TYPE=<custom name of the key type>` - sets the name of the custom key type that is used from the key-value APIs in Ignite. The name should correspond to a Java, .NET, or C++ class, or it can be a random one if link:data-modeling/data-modeling#binary-object-format[BinaryObjects] is used instead of a custom class. The number of fields and their types in the custom key type has to correspond to the `PRIMARY KEY`. Refer to the <<Use non-SQL API>> section below for more details.
65** `VALUE_TYPE=<custom name of the value type of the new cache>` - sets the name of a custom value type that is used from the key-value and other non-SQL APIs in Ignite. The name should correspond to a Java, .NET, or C++ class, or it can be a random one if
66link:data-modeling/data-modeling#binary-object-format[BinaryObjects] is used instead of a custom class. The value type should include all the columns defined in the CREATE TABLE command except for those listed in the `PRIMARY KEY` constraint. Refer to the <<Use non-SQL API>> section below for more details.
67Also, the same `VALUE_TYPE` is required to use SQL queries over data replicated with link:extensions-and-integrations/change-data-capture-extensions[CDC].
68** `WRAP_KEY=<true | false>` - this flag controls whether a _single column_ `PRIMARY KEY` should be wrapped in the link:data-modeling/data-modeling#binary-object-format[BinaryObjects] format or not. By default, this flag is set to false. This flag does not have any effect on the `PRIMARY KEY` with multiple columns; it always gets wrapped regardless of the value of the parameter.
69** `WRAP_VALUE=<true | false>` - this flag controls whether a single column value of a primitive type should be wrapped in the link:data-modeling/data-modeling#binary-object-format[BinaryObjects] format or not. By default, this flag is set to true. This flag does not have any effect on the value with multiple columns; it always gets wrapped regardless of the value of the parameter. Set this parameter to false if you have a single column value and do not plan to add additional columns to the table. Note that once the parameter is set to false, you can't use the `ALTER TABLE ADD COLUMN` command for this specific table.
70
71
72Read more about the database architecture on the link:SQL/sql-introduction[SQL Introduction] page.
73
74
75=== Define Primary Key
76
77The example below shows how to create a table with `PRIMARY KEY` specified in the column definition and override cache
78related parameters. A new distributed cache `SQL_PUBLIC_PERSON` will be created (the `SQL_{SCHEMA_NAME}_{TABLE}` format
79is used for naming) which stores objects of the `Person` type that corresponds to a specific Java, .NET, C++ class or BinaryObject.
80
81The distributed cache related parameters are passed in the `WITH` clause of the statement. If the `WITH` clause is omitted,
82then the cache will be created with default parameters set in the `CacheConfiguration` object.
83
84[source,sql]
85----
86CREATE TABLE Person (
87id int PRIMARY KEY,
88city_id int,
89name varchar,
90age int,
91company varchar
92) WITH "atomicity=transactional,cachegroup=somegroup";
93----
94
95
96=== Use non-SQL API
97
98If you wish to access the table data by the key-value or other non-SQL API, then you might be need to set the `CACHE_NAME` and
99`KEY_TYPE`, `VALUE_TYPE` parameters corresponding to your business model objects to make non-SQL APIs usage more convenient.
100
101- Use the `CACHE_NAME` parameter to override the default name with the following format `SQL_{SCHEMA_NAME}_{TABLE}`.
102- By default, the command also creates two new binary types - for the key and value respectively. Ignite in turn generates
103the names of the types randomly including a UUID string which complicates the usage of these types from a non-SQL API.
104
105The example below shows how to create a table `PERSON` and the underlying cache with the same name. The cache will store objects
106of the `Person` type with explicitly defined the key type `PersonKey` and value type `PersonValue`. The `PRIMARY KEY` columns will
107be used as the object's key, the rest of the columns will belong to the value.
108
109[source,sql]
110----
111CREATE TABLE IF NOT EXISTS Person (
112id int,
113city_id int,
114name varchar,
115age int,
116company varchar,
117PRIMARY KEY (id, city_id)
118) WITH "template=partitioned,backups=1,affinity_key=city_id,CACHE_NAME=Person,KEY_TYPE=PersonKey,VALUE_TYPE=PersonValue";
119----
120
121
122=== Use non-Upper Case Columns
123
124Ignite parses all unquoted identifiers, names of a table columns and converts them to uppercase
125during the `CREATE TABLE` command execution which, in turn, makes the command with explicitly defined key
126and value types a bit more challenging.
127
128There are a few options that might help you to deal with such a case:
129
130* Use link:SQL/sql-api[QuerySqlField] annotation. This will prevent checking the field non-UpperCase each time because of
131an alias for the column is created each time the `CREATE TABLE` command being executed.
132* Keeping in mind that column names converted each time to the upper case by default, you have to be sure that DDL fields
133and cache type fields are always match the letters case.
134
135In the example below you can see the usage of quotes for the `affKey` CamelCase field in the `CREATE TABLE` command with
136matching of the same field in the `PersonKey` cache key type.
137
138[source,sql]
139----
140CREATE TABLE IF NOT EXISTS Person (
141id INT,
142"affKey" INT,
143val VARCHAR,
144PRIMARY KEY (id, "affKey")
145) WITH "template=partitioned,backups=1,affinity_key=affKey,CACHE_NAME=Person,KEY_TYPE=PersonKey,VALUE_TYPE=PersonValue";
146----
147
148[source,java]
149----
150class PersonKey {
151private int id;
152
153/*
154* This is a camel case field 'affKey' must match the DDL table schema, so you must be sure:
155* - Using the quoted "affKey" field name in the DDL table definition;
156* - Convert the 'affKey' field to the upper case 'AFFKEY' to match the DDL table definition;
157*/
158@AffinityKeyMapped
159private int affKey;
160
161public PersonKey(int id, int affKey) {
162this.id = id;
163this.affKey = affKey;
164}
165}
166----
167
168Note that some integrations with the Apache Ignite like the link:extensions-and-integrations/spring/spring-data[Spring Data]
169`CrudRepository` doesn't support the quoted fields to access the data.
170
171
172== ALTER TABLE
173
174Modify the structure of an existing table.
175
176[source,sql]
177----
178ALTER TABLE [IF EXISTS] tableName {alter_specification}
179
180alter_specification:
181ADD [COLUMN] {[IF NOT EXISTS] tableColumn | (tableColumn [,...])}
182| DROP [COLUMN] {[IF EXISTS] columnName | (columnName [,...])}
183| {LOGGING | NOLOGGING}
184
185tableColumn := columnName columnType
186----
187
188[NOTE]
189====
190[discrete]
191=== Scope of ALTER TABLE
192Presently, Ignite only supports addition and removal of columns.
193====
194
195Parameters:
196
197- `tableName` - the name of the table.
198- `tableColumn` - the name and type of the column to be added to the table.
199- `columnName` - the name of the column to be added or removed.
200- `IF EXISTS` - if applied to TABLE, do not throw an error if a table with the specified table name does not exist. If applied to COLUMN, do not throw an error if a column with the specified name does not exist.
201- `IF NOT EXISTS` - do not throw an error if a column with the same name already exists.
202- `LOGGING` - enable link:persistence/native-persistence#write-ahead-log[write-ahead logging] for the table. Write-ahead logging in enabled by default. The command is relevant only if Ignite persistence is used.
203- `NOLOGGING` - disable write-ahead logging for the table. The command is relevant only if Ignite persistence is used.
204
205
206`ALTER TABLE ADD` adds a new column or several columns to a previously created table. Once a column is added, it can be accessed using link:sql-reference/dml[DML commands] and indexed with the <<CREATE INDEX>> statement.
207
208`ALTER TABLE DROP` removes an existing column or multiple columns from a table. Once a column is removed, it cannot be accessed within queries. Consider the following notes and limitations:
209
210- The command does not remove actual data from the cluster which means that if the column 'name' is dropped, the value of the 'name' is still stored in the cluster. This limitation is to be addressed in the next releases.
211- If the column was indexed, the index has to be dropped manually using the 'DROP INDEX' command.
212- It is not possible to remove a column that is a primary key or a part of such a key.
213- It is not possible to remove a column if it represents the whole value stored in the cluster. The limitation is relevant for primitive values.
214Ignite stores data in the form of key-value pairs and all the new columns will belong to the value. It's not possible to change a set of columns of the key (`PRIMARY KEY`).
215
216Both DDL and DML commands targeting the same table are blocked for a short time until `ALTER TABLE` is in progress.
217
218Schema changes applied by this command are persisted on disk if link:persistence/native-persistence[Ignite persistence] is enabled. Thus, the changes can survive full cluster restarts.
219
220
221Examples:
222
223Add a column to the table:
224
225[source,sql]
226----
227ALTER TABLE Person ADD COLUMN city varchar;
228----
229
230
231Add a new column to the table only if a column with the same name does not exist:
232
233[source,sql]
234----
235ALTER TABLE City ADD COLUMN IF NOT EXISTS population int;
236----
237
238
239Add a column only if the table exists:
240
241[source,sql]
242----
243ALTER TABLE IF EXISTS Missing ADD number long;
244----
245
246
247Add several columns to the table at once:
248
249
250[source,sql]
251----
252ALTER TABLE Region ADD COLUMN (code varchar, gdp double);
253----
254
255
256Drop a column from the table:
257
258
259[source,sql]
260----
261ALTER TABLE Person DROP COLUMN city;
262----
263
264
265Drop a column from the table only if a column with the same name does exist:
266
267
268[source,sql]
269----
270ALTER TABLE Person DROP COLUMN IF EXISTS population;
271----
272
273
274Drop a column only if the table exists:
275
276
277[source,sql]
278----
279ALTER TABLE IF EXISTS Person DROP COLUMN number;
280----
281
282
283Drop several columns from the table at once:
284
285
286[source,sql]
287----
288ALTER TABLE Person DROP COLUMN (code, gdp);
289----
290
291
292Disable write-ahead logging:
293
294
295[source,sql]
296----
297ALTER TABLE Person NOLOGGING
298----
299
300
301== DROP TABLE
302
303The `DROP TABLE` command drops an existing table.
304The underlying cache with all the data in it is destroyed, too.
305
306
307[source,sql]
308----
309DROP TABLE [IF EXISTS] tableName
310----
311
312Parameters:
313
314- `tableName` - the name of the table.
315- `IF NOT EXISTS` - do not throw an error if a table with the same name does not exist.
316
317
318Both DDL and DML commands targeting the same table are blocked while the `DROP TABLE` is in progress.
319Once the table is dropped, all pending commands will fail with appropriate errors.
320
321Schema changes applied by this command are persisted on disk if link:persistence/native-persistence[Ignite persistence] is enabled. Thus, the changes can survive full cluster restarts.
322
323Examples:
324
325Drop Person table if the one exists:
326
327[source,sql]
328----
329DROP TABLE IF EXISTS "Person";
330----
331
332== CREATE INDEX
333
334Create an index on the specified table.
335
336[source,sql]
337----
338CREATE [SPATIAL] INDEX [[IF NOT EXISTS] indexName] ON tableName
339(columnName [ASC|DESC] [,...]) [(index_option [...])]
340
341index_option := {INLINE_SIZE size | PARALLEL parallelism_level}
342----
343
344Parameters:
345
346* `indexName` - the name of the index to be created. The index name must be unique per schema.
347* `ASC` - specifies ascending sort order (default).
348* `DESC` - specifies descending sort order.
349* `SPATIAL` - create the spatial index. Presently, only geometry types are supported.
350* `IF NOT EXISTS` - do not throw an error if an index with the same name already exists. The database checks indexes' names only, and does not consider columns types or count. The index creation will be skipped if an index with the same name exist in the schema.
351* `index_option` - additional options for index creation:
352** `INLINE_SIZE` - specifies index inline size in bytes. Depending on the size, Ignite will place the whole indexed value or a part of it directly into index pages, thus omitting extra calls to data pages and increasing queries' performance. Index inlining is enabled by default and the size is pre-calculated automatically based on the table structure. To disable inlining, set the size to 0 (not recommended). Refer to the link:SQL/sql-tuning#increasing-index-inline-size[Increasing Index Inline Size] section for more details.
353** `PARALLEL` - specifies the number of threads to be used in parallel for index creation. The greater number is set, the faster the index is created and built. If the value exceeds the number of CPUs, then it will be decreased to the number of cores. If the parameter is not specified, then the number of threads is calculated as 25% of the CPU cores available.
354
355
356`CREATE INDEX` creates a new index on the specified table. Regular indexes are stored in the internal B+tree data structures. The B+tree gets distributed across the cluster along with the actual data. A cluster node stores a part of the index for the data it owns.
357
358If `CREATE INDEX` is executed in runtime on live data then the database will iterate over the specified columns synchronously indexing them. The rest of the DDL commands targeting the same table are blocked until CREATE INDEX is in progress. DML command execution is not affected and can be performed in parallel.
359
360Schema changes applied by this command are persisted on disk if link:persistence/native-persistence[Ignite persistence] is enabled. Thus, the changes can survive full cluster restarts.
361
362
363
364=== Indexes Tradeoffs
365There are multiple things you should consider when choosing indexes for your application.
366
367- Indexes are not free. They consume memory, and each index needs to be updated separately, thus the performance of write operations might drop if too many indexes are created. On top of that, if a lot of indexes are defined, the optimizer might make more mistakes by choosing the wrong index while building the execution plan.
368+
369WARNING: It is poor strategy to index everything.
370
371- Indexes are just sorted data structures (B+tree). If you define an index for the fields (a,b,c) then the records will be sorted first by a, then by b and only then by c.
372+
373[NOTE]
374====
375[discrete]
376=== Example of Sorted Index
377[width="25%" cols="33l, 33l, 33l"]
378|=====
379| A | B | C
380| 1 | 2 | 3
381| 1 | 4 | 2
382| 1 | 4 | 4
383| 2 | 3 | 5
384| 2 | 4 | 4
385| 2 | 4 | 5
386|=====
387
388Any condition like `a = 1 and b > 3` can be viewed as a bounded range, both bounds can be quickly looked up in *log(N)* time, the result will be everything between.
389
390The following conditions will be able to use the index:
391
392- `a = ?`
393- `a = ? and b = ?`
394- `a = ? and b = ? and c = ?`
395
396Condition `a = ? and c = ?` is no better than `a = ?` from the index point of view.
397Obviously half-bounded ranges like `a > ?` can be used as well.
398====
399
400- Indexes on single fields are no better than group indexes on multiple fields starting with the same field (index on (a) is no better than (a,b,c)). Thus it is preferable to use group indexes.
401
402- When `INLINE_SIZE` option is specified, indexes holds a prefix of field data in the B+tree pages. This improves search performance by doing less row data retrievals, however substantially increases size of the tree (with a moderate increase in tree height) and reduces data insertion and removal performance due to excessive page splits and merges. It's a good idea to consider page size when choosing inlining size for the tree: each B-tree entry requires `16 + inline-size` bytes in the page (plus header and extra links for the page).
403
404
405Examples:
406
407Create a regular index:
408
409[source,sql]
410----
411CREATE INDEX title_idx ON books (title);
412----
413
414Create a descending index only if it does not exist:
415
416[source,sql]
417----
418CREATE INDEX IF NOT EXISTS name_idx ON persons (firstName DESC);
419----
420
421Create a composite index:
422
423[source,sql]
424----
425CREATE INDEX city_idx ON sales (country, city);
426----
427
428Create an index specifying data inline size:
429
430[source,sql]
431----
432CREATE INDEX fast_city_idx ON sales (country, city) INLINE_SIZE 60;
433----
434
435Create a geospatial index:
436
437[source,sql]
438----
439CREATE SPATIAL INDEX idx_person_address ON Person (address);
440----
441
442
443== DROP INDEX
444
445`DROP INDEX` deletes an existing index.
446
447
448[source,sql]
449----
450DROP INDEX [IF EXISTS] indexName
451----
452
453Parameters:
454
455* `indexName` - the name of the index to drop.
456* `IF EXISTS` - do not throw an error if an index with the specified name does not exist. The database checks indexes' names only not considering column types or count.
457
458
459DDL commands targeting the same table are blocked until `DROP INDEX` is in progress. DML command execution is not affected and can be performed in parallel.
460
461Schema changes applied by this command are persisted on disk if link:persistence/native-persistence[Ignite persistence] is enabled. Thus, the changes can survive full cluster restarts.
462
463
464[discrete]
465=== Examples
466Drop an index:
467
468
469[source,sql]
470----
471DROP INDEX idx_person_name;
472----
473
474
475== CREATE USER
476
477The command creates a user with a given name and password.
478
479A new user can only be created using a superuser account when authentication for thin clients is enabled. Ignite creates the superuser account under the name `ignite` and password `ignite` on the first cluster start-up. Presently, you can't rename the superuser account nor grant its privileges to any other account.
480
481
482
483[source,sql]
484----
485CREATE USER userName WITH PASSWORD 'password';
486----
487
488Parameters:
489
490* `userName` - new user's name. The name cannot be longer than 60 bytes in UTF8 encoding.
491* `password` - new user's password. An empty password is not allowed.
492
493To create a _case-sensitive_ username, use the quotation (") SQL identifier.
494
495[NOTE]
496====
497[discrete]
498=== When Are Case-Sensitive Names Preferred?
499The case-insensitivity property of the usernames is supported for JDBC and ODBC interfaces only. If it's planned to access Ignite from Java, .NET, or other programming language APIs then the username has to be passed either in all upper-case letters or enclosed in double quotes (") from those interfaces.
500
501For instance, if `Test` was set as a username then:
502
503- You can use `Test`, `TEst`, `TEST` and other combinations from JDBC and ODBC.
504- You can use either `TEST` or `"Test"` as the username from Ignite's native SQL APIs designed for Java, .NET and other programming languages.
505
506Alternatively, use the case-sensitive username at all times to ensure name consistency across all the SQL interfaces.
507====
508
509Examples:
510
511Create a new user using test as a name and password:
512
513
514[source,sql]
515----
516CREATE USER test WITH PASSWORD 'test';
517----
518
519Create a case-sensitive username:
520
521
522[source,sql]
523----
524CREATE USER "TeSt" WITH PASSWORD 'test'
525----
526
527
528== ALTER USER
529
530The command changes an existing user's password.
531The password can be updated by the superuser (`ignite`, see <<CREATE USER>> for more details) or by the user themselves.
532
533
534[source,sql]
535----
536ALTER USER userName WITH PASSWORD 'newPassword';
537----
538
539
540Parameters:
541
542* `userName` - existing user's name.
543* `newPassword` - the new password to set for the user's account.
544
545
546Examples:
547
548Updating user's password:
549
550
551[source,sql]
552----
553ALTER USER test WITH PASSWORD 'test123';
554----
555
556
557== DROP USER
558
559The command removes an existing user.
560
561The user can be removed only by the superuser (`ignite`, see <<CREATE USER>> for more details).
562
563
564[source,sql]
565----
566DROP USER userName;
567----
568
569
570Parameters:
571
572* `userName` - a name of the user to remove.
573
574
575Examples:
576
577[source,sql]
578----
579DROP USER test;
580----
581
582== ANALYZE
583
584The ANALYZE command collects link:SQL/sql-statistics[statistics,window=_blank].
585
586[source,sql]
587----
588ANALYZE 'schemaName'.'tableName'(column1, column2);
589----
590
591Parameters:
592
593* `schemaName` - a name of the schema to collect statistics for.
594* `tableName` - a name of the table to collect statistics for.
595* `(column1, column2)` - names of the columns to collect statistics for.
596
597image::images/svg/analyze_bnf1.svg[Embedded,opts=inline]
598
599image::images/svg/analyze_bnf2.svg[Embedded,opts=inline]
600
601When the ANALYZE command is used with `with` parameters statement, specified parameters are applied for every target. For example:
602
603[source,sql]
604----
605ANALYZE public.statistics_test, statistics_test2, statistics_test3(col3) WITH 'MAX_CHANGED_PARTITION_ROWS_PERCENT=15,NULLS=0'
606----
607
608Possible parameters:
609
610* MAX_CHANGED_PARTITION_ROWS_PERCENT - Maximum percentage of outdated rows in the table (the default value is 15%). See the link:SQL/sql-statistics#statistics-obsolescence[SQL Statistics,window=_blank] page for more details.
611* NULLS - Number of null values in column.
612* TOTAL - Total number of column values.
613* SIZE - Average size of column values (in bytes).
614* DISTINCT - Number of distinct non-null values in column.
615
616== REFRESH STATISTICS
617
618The command refreshes link:SQL/sql-statistics[statistics,window=_blank].
619
620[source,sql]
621----
622REFRESH STATISTICS 'schemaName'.'tableName'(column1, column2);
623----
624
625Parameters:
626
627* `schemaName` - a name of the schema to refresh statistics for.
628* `tableName` - a name of the table to refresh statistics for.
629* `(column1, column2)` - names of the columns to refresh statistics for.
630
631image::images/svg/refresh_bnf.svg[Embedded,opts=inline]
632
633Example:
634
635[source,sql]
636----
637REFRESH STATISTICS PRODUCTS, SALE(productId, discount)
638----
639
640== DROP STATISTICS
641
642The command drops link:SQL/sql-statistics[statistics,window=_blank].
643
644[source,sql]
645----
646DROP STATISTICS 'schemaName'.'tableName'(column1, column2);
647----
648
649Parameters:
650
651* `schemaName` - a name of the schema to drop statistics for.
652* `tableName` - a name of the table to drop statistics for.
653* `(column1, column2)` - names of the columns to drop statistics for.
654
655image::images/svg/drop_bnf.svg[Embedded,opts=inline]
656
657Example:
658
659[source,sql]
660----
661DROP STATISTICS USERS, ORDERS(customerId, productId)
662----
663
664
665