X
CREATE TABLE grass_test1 (i1 INTEGER, d1 DOUBLE PRECISION, c1 VARCHAR(20))

X
INSERT INTO grass_test1 VALUES ( 1, 123.456, 'abcd' )

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INSERT INTO grass_test1 VALUES ( 2, null, 'xxx' )

S
SELECT * FROM grass_test1
1|123.456|abcd
2||xxx

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SELECT c1 FROM grass_test1 WHERE d1 < 500 / 2 AND i1 <> 2  AND c1 LIKE '%bc%' 
abcd

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INSERT INTO grass_test1 VALUES ( 3, 0.0, '_\''_' )

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ALTER TABLE grass_test1 ADD COLUMN i2 INTEGER

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UPDATE grass_test1 SET d1 = 18.6, i2 = 987  WHERE i1 = 2

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SELECT * FROM grass_test1
1|123.456|abcd|
2|18.6|xxx|987
3|0|_\'_|

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DROP TABLE grass_test1