Paramètres de session

INSERT INTO table_1 VALUES (1, 'a'), (2, 'bb'), (3, 'ccc'), (4, 'dddd');
SElECT * FROM table_1;

┌─x─┬─y────┐
│ 1 │ a    │
│ 2 │ bb   │
│ 3 │ ccc  │
│ 4 │ dddd │
└───┴──────┘

SELECT *
FROM table_1
SETTINGS additional_result_filter = 'x != 2'

┌─x─┬─y────┐
│ 1 │ a    │
│ 3 │ ccc  │
│ 4 │ dddd │
└───┴──────┘

INSERT INTO table_1 VALUES (1, 'a'), (2, 'bb'), (3, 'ccc'), (4, 'dddd');
SELECT * FROM table_1;

┌─x─┬─y────┐
│ 1 │ a    │
│ 2 │ bb   │
│ 3 │ ccc  │
│ 4 │ dddd │
└───┴──────┘

SELECT *
FROM table_1
SETTINGS additional_table_filters = {'table_1': 'x != 2'}

┌─x─┬─y────┐
│ 1 │ a    │
│ 3 │ ccc  │
│ 4 │ dddd │
└───┴──────┘

CREATE TABLE example (
    user_id UInt64,
    avg_session_length AggregateFunction(avg, UInt32)
);

INSERT INTO example FORMAT CSV
123,456

INSERT INTO example FORMAT CSV
123,"[456,789,101]"

SELECT SUM(-1), MAX(0) FROM system.one WHERE 0;

┌─SUM(-1)─┬─MAX(0)─┐
│       0 │      0 │
└─────────┴────────┘

┌─SUMOrNull(-1)─┬─MAXOrNull(0)─┐
│          NULL │         NULL │
└───────────────┴──────────────┘

<profiles>
    <default>
        <allow_nondeterministic_mutations>1</allow_nondeterministic_mutations>

        <!-- ... -->
    </default>

    <!-- ... -->

</profiles>

INSERT INTO FUNCTION null('foo String') SETTINGS max_threads=1 VALUES ('bar');

SET allow_settings_after_format_in_insert=1;
INSERT INTO FUNCTION null('foo String') VALUES ('bar') SETTINGS max_threads=1;

CREATE TABLE test(a Int64, d Date, s String) ENGINE = MergeTree PARTITION BY toYYYYMDECLARE(d) ORDER BY a;
INSERT INTO test VALUES(1, '2021-01-01', '');
INSERT INTO test VALUES(1, '2021-01-01', '');
ALTER TABLE test DETACH PARTITION ID '202101';

ALTER TABLE test ATTACH PARTITION ID '202101' SETTINGS alter_partition_verbose_result = 1;

┌─command_type─────┬─partition_id─┬─part_name────┬─old_part_name─┐
│ ATTACH PARTITION │ 202101       │ 202101_7_7_0 │ 202101_5_5_0  │
│ ATTACH PARTITION │ 202101       │ 202101_8_8_0 │ 202101_6_6_0  │
└──────────────────┴──────────────┴──────────────┴───────────────┘

ALTER TABLE test FREEZE SETTINGS alter_partition_verbose_result = 1;

┌─command_type─┬─partition_id─┬─part_name────┬─backup_name─┬─backup_path───────────────────┬─part_backup_path────────────────────────────────────────────┐
│ FREEZE ALL   │ 202101       │ 202101_7_7_0 │ 8           │ /var/lib/clickhouse/shadow/8/ │ /var/lib/clickhouse/shadow/8/data/default/test/202101_7_7_0 │
│ FREEZE ALL   │ 202101       │ 202101_8_8_0 │ 8           │ /var/lib/clickhouse/shadow/8/ │ /var/lib/clickhouse/shadow/8/data/default/test/202101_8_8_0 │
└──────────────┴──────────────┴──────────────┴─────────────┴───────────────────────────────┴─────────────────────────────────────────────────────────────┘

SET cast_keep_nullable = 0;
SELECT CAST(toNullable(toInt32(0)) AS Int32) as x, toTypeName(x);

┌─x─┬─toTypeName(CAST(toNullable(toInt32(0)), 'Int32'))─┐
│ 0 │ Int32                                             │
└───┴───────────────────────────────────────────────────┘

SET cast_keep_nullable = 1;
SELECT CAST(toNullable(toInt32(0)) AS Int32) as x, toTypeName(x);

┌─x─┬─toTypeName(CAST(toNullable(toInt32(0)), 'Int32'))─┐
│ 0 │ Nullable(Int32)                                   │
└───┴───────────────────────────────────────────────────┘

EXPLAIN SYNTAX
SELECT *
FROM
(
    SELECT number AS x
    FROM numbers(20)
) AS a
WHERE ((x >= 1) AND (x <= 5)) OR ((x >= 10) AND (x <= 15))
SETTINGS convert_query_to_cnf = false;

┌─explain────────────────────────────────────────────────────────┐
│ SELECT x                                                       │
│ FROM                                                           │
│ (                                                              │
│     SELECT number AS x                                         │
│     FROM numbers(20)                                           │
│     WHERE ((x >= 1) AND (x <= 5)) OR ((x >= 10) AND (x <= 15)) │
│ ) AS a                                                         │
│ WHERE ((x >= 1) AND (x <= 5)) OR ((x >= 10) AND (x <= 15))     │
│ SETTINGS convert_query_to_cnf = 0                              │
└────────────────────────────────────────────────────────────────┘

EXPLAIN SYNTAX
SELECT *
FROM
(
    SELECT number AS x
    FROM numbers(20)
) AS a
WHERE ((x >= 1) AND (x <= 5)) OR ((x >= 10) AND (x <= 15))
SETTINGS convert_query_to_cnf = true;

┌─explain───────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
│ SELECT x                                                                                                              │
│ FROM                                                                                                                  │
│ (                                                                                                                     │
│     SELECT number AS x                                                                                                │
│     FROM numbers(20)                                                                                                  │
│     WHERE ((x <= 15) OR (x <= 5)) AND ((x <= 15) OR (x >= 1)) AND ((x >= 10) OR (x <= 5)) AND ((x >= 10) OR (x >= 1)) │
│ ) AS a                                                                                                                │
│ WHERE ((x >= 10) OR (x >= 1)) AND ((x >= 10) OR (x <= 5)) AND ((x <= 15) OR (x >= 1)) AND ((x <= 15) OR (x <= 5))     │
│ SETTINGS convert_query_to_cnf = 1                                                                                     │
└───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

SET default_table_engine = 'Log';

SELECT name, value, changed FROM system.settings WHERE name = 'default_table_engine';

┌─name─────────────────┬─value─┬─changed─┐
│ default_table_engine │ Log   │       1 │
└──────────────────────┴───────┴─────────┘

CREATE TABLE my_table (
    x UInt32,
    y UInt32
);

SHOW CREATE TABLE my_table;

┌─statement────────────────────────────────────────────────────────────────┐
│ CREATE TABLE default.my_table
(
    `x` UInt32,
    `y` UInt32
)
ENGINE = Log
└──────────────────────────────────────────────────────────────────────────┘

SET default_temporary_table_engine = 'Log';

CREATE TEMPORARY TABLE my_table (
    x UInt32,
    y UInt32
);

SHOW CREATE TEMPORARY TABLE my_table;

┌─statement────────────────────────────────────────────────────────────────┐
│ CREATE TEMPORARY TABLE default.my_table
(
    `x` UInt32,
    `y` UInt32
)
ENGINE = Log
└──────────────────────────────────────────────────────────────────────────┘

SELECT *
FROM remote('127.0.0.{2,3}', system.one)
GROUP BY dummy
LIMIT 1
SETTINGS distributed_group_by_no_merge = 1
FORMAT PrettyCompactMonoBlock

┌─dummy─┐
│     0 │
│     0 │
└───────┘

SELECT *
FROM remote('127.0.0.{2,3}', system.one)
GROUP BY dummy
LIMIT 1
SETTINGS distributed_group_by_no_merge = 2
FORMAT PrettyCompactMonoBlock

┌─dummy─┐
│     0 │
└───────┘

CREATE TABLE TAB(C1 Int, C2 Int, ALL Int) ENGINE=Memory();

INSERT INTO TAB VALUES (10, 20, 30), (20, 20, 10), (30, 10, 20);

SELECT * FROM TAB ORDER BY ALL; -- returns an error that ALL is ambiguous

SELECT * FROM TAB ORDER BY ALL SETTINGS enable_order_by_all = 0;

┌─C1─┬─C2─┬─ALL─┐
│ 20 │ 20 │  10 │
│ 30 │ 10 │  20 │
│ 10 │ 20 │  30 │
└────┴────┴─────┘

CREATE TABLE positional_arguments(one Int, two Int, three Int) ENGINE=Memory();

INSERT INTO positional_arguments VALUES (10, 20, 30), (20, 20, 10), (30, 10, 20);

SELECT * FROM positional_arguments ORDER BY 2,3;

┌─one─┬─two─┬─three─┐
│  30 │  10 │   20  │
│  20 │  20 │   10  │
│  10 │  20 │   30  │
└─────┴─────┴───────┘

SELECT
    count()
FROM events
WHERE (_part, _part_offset) IN (
    SELECT _part, _part_offset
    FROM events
    WHERE user_id = 42
)

CREATE TABLE tab
(
    a UInt64,
    b UInt64,
    INDEX idx_a a TYPE minmax,
    INDEX idx_b b TYPE set(3)
)
ENGINE = MergeTree ORDER BY tuple();

SET exclude_materialize_skip_indexes_on_insert='idx_a'; -- idx_a will be not be updated upon insert
--SET exclude_materialize_skip_indexes_on_insert='idx_a, idx_b'; -- neither index would be updated on insert

INSERT INTO tab SELECT number, number / 50 FROM numbers(100); -- only idx_b is updated

-- since it is a session setting it can be set on a per-query level
INSERT INTO tab SELECT number, number / 50 FROM numbers(100, 100) SETTINGS exclude_materialize_skip_indexes_on_insert='idx_b';

ALTER TABLE tab MATERIALIZE INDEX idx_a; -- this query can be used to explicitly materialize the index

SET exclude_materialize_skip_indexes_on_insert = DEFAULT; -- reset setting to default

CREATE TABLE test
(
    key Int64,
    some String
)
ENGINE = ReplacingMergeTree
ORDER BY key;

INSERT INTO test FORMAT Values (1, 'first');
INSERT INTO test FORMAT Values (1, 'second');

SELECT * FROM test;
┌─key─┬─some───┐
│   1 │ second │
└─────┴────────┘
┌─key─┬─some──┐
│   1 │ first │
└─────┴───────┘

SELECT * FROM test SETTINGS final = 1;
┌─key─┬─some───┐
│   1 │ second │
└─────┴────────┘

SET final = 1;
SELECT * FROM test;
┌─key─┬─some───┐
│   1 │ second │
└─────┴────────┘

SET flatten_nested = 1;
CREATE TABLE t_nest (`n` Nested(a UInt32, b UInt32)) ENGINE = MergeTree ORDER BY tuple();

SHOW CREATE TABLE t_nest;

┌─statement───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
│ CREATE TABLE default.t_nest
(
    `n.a` Array(UInt32),
    `n.b` Array(UInt32)
)
ENGINE = MergeTree
ORDER BY tuple()
SETTINGS index_granularity = 8192 │
└─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

SET flatten_nested = 0;

CREATE TABLE t_nest (`n` Nested(a UInt32, b UInt32)) ENGINE = MergeTree ORDER BY tuple();

SHOW CREATE TABLE t_nest;

┌─statement──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
│ CREATE TABLE default.t_nest
(
    `n` Nested(a UInt32, b UInt32)
)
ENGINE = MergeTree
ORDER BY tuple()
SETTINGS index_granularity = 8192 │
└────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘