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65 lines
1.3 KiB
Plaintext
65 lines
1.3 KiB
Plaintext
CREATE TABLE t1(
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id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
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a CHAR(1) NOT NULL,
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b CHAR(36) NOT NULL) ENGINE=InnoDB;
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INSERT INTO t1(a,b) VALUES ('a','b');
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INSERT INTO t1(a,b) SELECT a,b FROM t1;
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INSERT INTO t1(a,b) SELECT a,b FROM t1;
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INSERT INTO t1(a,b) SELECT a,b FROM t1;
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INSERT INTO t1(a,b) SELECT a,b FROM t1;
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ALTER TABLE t1 ADD KEY (a);
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affected rows: 0
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info: Records: 0 Duplicates: 0 Warnings: 0
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EXPLAIN SELECT COUNT(*) FROM t1, t1 t2 WHERE t1.a = t2.a AND t1.b = t2.b;
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id 1
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select_type SIMPLE
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table t1
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type ALL
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possible_keys a
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key NULL
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key_len NULL
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ref NULL
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rows 16
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Extra
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id 1
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select_type SIMPLE
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table t2
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type ref
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possible_keys a
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key a
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key_len 1
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ref test.t1.a
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rows 1
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Extra Using where
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ALTER TABLE t1 DROP KEY a;
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SET expand_fast_index_creation = 1;
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SELECT @@expand_fast_index_creation;
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@@expand_fast_index_creation
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1
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ALTER TABLE t1 ADD KEY (a);
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affected rows: 0
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info: Records: 0 Duplicates: 0 Warnings: 0
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EXPLAIN SELECT COUNT(*) FROM t1, t1 t2 WHERE t1.a = t2.a AND t1.b = t2.b;
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id 1
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select_type SIMPLE
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table t1
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type ALL
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possible_keys a
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key NULL
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key_len NULL
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ref NULL
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rows 16
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Extra
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id 1
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select_type SIMPLE
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table t2
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type ALL
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possible_keys a
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key NULL
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key_len NULL
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ref NULL
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rows 16
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Extra Using where; Using join buffer
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SET expand_fast_index_creation = 0;
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DROP TABLE t1;
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