CREATE VIEW

CREATE [OR REPLACE] VIEW [IF NOT EXISTS] [db.]table_name [(alias1 [, alias2 ...])] [ON CLUSTER cluster_name]
[DEFINER = { user | CURRENT_USER }] [SQL SECURITY { DEFINER | INVOKER | NONE }]
AS SELECT ...
[COMMENT 'comment']

CREATE VIEW view AS SELECT ...

SELECT a, b, c FROM view

SELECT a, b, c FROM (SELECT ...)

CREATE VIEW view AS SELECT * FROM TABLE WHERE Column1={column1:datatype1} and Column2={column2:datatype2} ...

SELECT * FROM view(column1=value1, column2=value2 ...)

DESCRIBE view(column1=value1, column2=value2 ...)

CREATE MATERIALIZED VIEW [IF NOT EXISTS] [db.]table_name [ON CLUSTER cluster_name] [TO[db.]name [(columns)]] [ENGINE = engine] [POPULATE]
[REFRESH ...]
[DEFINER = { user | CURRENT_USER }] [SQL SECURITY { DEFINER | NONE }]
AS SELECT ...
[COMMENT 'comment']

CREATE OR REPLACE MATERIALIZED VIEW [db.]table_name [ON CLUSTER cluster_name] [TO[db.]name [(columns)]] [ENGINE = engine] [POPULATE]
[REFRESH ...]
[DEFINER = { user | CURRENT_USER }] [SQL SECURITY { DEFINER | NONE }]
AS SELECT ...
[COMMENT 'comment']

CREATE OR REPLACE MATERIALIZED VIEW [db.]name [ON CLUSTER cluster]
[TO [db.]target_table]
[ENGINE = engine]
[POPULATE]
[REFRESH ...]
AS SELECT ...

-- Create a materialized view with an inner table
CREATE OR REPLACE MATERIALIZED VIEW mv
    ENGINE = MergeTree ORDER BY x
    AS SELECT x, sum(y) AS total FROM src GROUP BY x;

-- Replace with a new definition (old inner table data is lost)
CREATE OR REPLACE MATERIALIZED VIEW mv
    ENGINE = MergeTree ORDER BY x
    AS SELECT x, count() AS cnt FROM src GROUP BY x;

-- Replace with POPULATE to backfill from existing source data
CREATE OR REPLACE MATERIALIZED VIEW mv
    ENGINE = MergeTree ORDER BY x
    POPULATE
    AS SELECT x FROM src;

-- Replace an inner-table MV with a TO-table MV (target data is preserved)
CREATE OR REPLACE MATERIALIZED VIEW mv TO target
    AS SELECT x FROM src;

ALTER TABLE MODIFY SQL SECURITY { DEFINER | INVOKER | NONE } [DEFINER = { user | CURRENT_USER }]

CREATE VIEW test_view
DEFINER = alice SQL SECURITY DEFINER
AS SELECT ...

CREATE VIEW test_view
SQL SECURITY INVOKER
AS SELECT ...

CREATE MATERIALIZED VIEW [IF NOT EXISTS] [db.]table_name [ON CLUSTER cluster]
REFRESH [EVERY|AFTER interval [OFFSET interval]]
[RANDOMIZE FOR interval]
[DEPENDS ON [db.]name [, [db.]name [, ...]]]
[SETTINGS name = value [, name = value [, ...]]]
[APPEND [INCREMENTAL]]
[TO[db.]name] [(columns)] [ENGINE = engine]
[EMPTY]
[DEFINER = { user | CURRENT_USER }] [SQL SECURITY { DEFINER | NONE }]
AS SELECT ...
[COMMENT 'comment']

number SECOND|MINUTE|HOUR|DAY|WEEK|MONTH|YEAR

REFRESH EVERY 1 DAY -- every day, at midnight (UTC)
REFRESH EVERY 1 MONTH -- on 1st day of every month, at midnight
REFRESH EVERY 1 MONTH OFFSET 5 DAY 2 HOUR -- on 6th day of every month, at 2:00 am
REFRESH EVERY 2 WEEK OFFSET 5 DAY 15 HOUR 10 MINUTE -- every other Saturday, at 3:10 pm
REFRESH EVERY 30 MINUTE -- at 00:00, 00:30, 01:00, 01:30, etc
REFRESH AFTER 30 MINUTE -- 30 minutes after the previous refresh completes, no alignment with time of day
-- REFRESH AFTER 1 HOUR OFFSET 1 MINUTE -- syntax error, OFFSET is not allowed with AFTER
REFRESH EVERY 1 WEEK 2 DAYS -- every 9 days, not on any particular day of the week or month;
                            -- specifically, when day number (since 1969-12-29) is divisible by 9
REFRESH EVERY 5 MONTHS -- every 5 months, different months each year (as 12 is not divisible by 5);
                       -- specifically, when month number (since 1970-01) is divisible by 5

REFRESH EVERY 1 DAY OFFSET 2 HOUR RANDOMIZE FOR 1 HOUR -- every day at random time between 01:30 and 02:30

CREATE MATERIALIZED VIEW dependent REFRESH EVERY 1 HOUR DEPENDS ON dependency [...]

CREATE MATERIALIZED VIEW dependent REFRESH AFTER 0 SECOND DEPENDS ON dependency [...]

CREATE MATERIALIZED VIEW dependent REFRESH DEPENDS ON dependency [...]

           10:00            11:00            12:00
           │                │                │
  X:        [run]┐           [run]┐           [run]┐
                 │                │                │
  Y:             └►[run]          └►[run]          └►[run]

           10:00          11:00          12:00          13:00
           │              │              │              |
  X:        [run]┐         [run]┐         [run]┐         [run]┐
                 │              └────┐    (Y skips 12:00)     └───┐
  Y:             └►[10:00 ru------un]└►[11:00 ru---------------un]└►[13:00 run]

            source
               │
               ▼
          ┌─────────┐
     ┌───►│    X    │◄───┐
     │    └──┬───┬──┘    │
  DEPENDS    │   │    DEPENDS
    ON       ▼   ▼      ON
     │      ┌─┐ ┌─┐      │
     └──────┤Y│ │Z├──────┘
            └─┘ └─┘

CREATE TABLE current_batch (t UInt64, v Int64) ENGINE ReplicatedMergeTree ORDER BY t;
CREATE TABLE batch_log (max_t UInt64, n Int64, v_sum Int64, processed_at DateTime64) ENGINE ReplicatedMergeTree ORDER BY max_t;
CREATE TABLE stats (h UInt64, n UInt64) ENGINE ReplicatedSummingMergeTree ORDER BY h;

-- (system.numbers stands in for a data source with monotonically increasing timestamps or sequence numbers)
CREATE MATERIALIZED VIEW current_batch_v REFRESH EVERY 10 SECOND DEPENDS ON batch_log_v, stats_v TO current_batch AS SELECT number as t, number * 10 as v FROM system.numbers WHERE number > (SELECT max(max_t) FROM batch_log) LIMIT 100;

CREATE MATERIALIZED VIEW batch_log_v REFRESH DEPENDS ON current_batch_v APPEND TO batch_log AS SELECT max(t) as max_t, count() as n, sum(v) as v_sum, now64() as processed_at FROM current_batch;

CREATE MATERIALIZED VIEW stats_v REFRESH DEPENDS ON current_batch_v APPEND TO stats AS SELECT cityHash64(v) % 20 as h, count() as n FROM current_batch GROUP BY h;

-- Must trigger initial refresh manually.
SYSTEM REFRESH VIEW current_batch_v;

ALTER TABLE [db.]name MODIFY REFRESH EVERY|AFTER ... [RANDOMIZE FOR ...] [DEPENDS ON ...] [SETTINGS ...]

-- Change the schedule, drop existing settings and dependencies.
ALTER TABLE rmv MODIFY REFRESH EVERY 30 MINUTE;

-- Change the schedule and tune retry behavior.
ALTER TABLE rmv MODIFY REFRESH EVERY 30 MINUTE
SETTINGS refresh_retries = 5,
         refresh_retry_initial_backoff_ms = 500,
         refresh_retry_max_backoff_ms = 60000;

-- Keep the dependency while changing the period.
ALTER TABLE rmv MODIFY REFRESH EVERY 6 HOUR DEPENDS ON other_rmv;

-- Drop the dependency by omitting `DEPENDS ON`.
ALTER TABLE rmv MODIFY REFRESH EVERY 6 HOUR;

CREATE TEMPORARY VIEW [IF NOT EXISTS] view_name AS <select_query>

CREATE TEMPORARY TABLE t_src (id UInt32, val String);
INSERT INTO t_src VALUES (1, 'a'), (2, 'b');

CREATE TEMPORARY VIEW tview AS
SELECT id, upper(val) AS u
FROM t_src
WHERE id <= 2;

SELECT * FROM tview ORDER BY id;

SHOW CREATE TEMPORARY VIEW tview;

DROP TEMPORARY VIEW IF EXISTS tview;  -- 临时视图使用 TEMPORARY TABLE 语法进行删除

-- A session-scoped, in-memory table
CREATE TEMPORARY TABLE temp_ids (id UInt64) ENGINE = Memory;

INSERT INTO temp_ids VALUES (1), (5), (42);

-- A session-scoped view over the temp table (purely logical)
CREATE TEMPORARY VIEW v_ids AS
SELECT id FROM temp_ids;

-- Replace 'test' with your cluster name.
-- GLOBAL JOIN forces ClickHouse to *ship* the small join-side (temp_ids via v_ids)
-- to every remote server that executes the left side.
SELECT count()
FROM cluster('test', system.numbers) AS n
GLOBAL ANY INNER JOIN v_ids USING (id)
WHERE n.number < 100;