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The structure of the data table used in this article is as follows:

The contents of the data table are as follows:

1. Arithmetic

1. Arithmetic

1.1 Operation of addition, subtraction, multiplication and division

SELECT
id,
(sales_a + sales_b)as all_sales,
(sales_a - sales_b)as sales_a_b,
(sales_a * price_a + sales_b * price_b)as gmv,
(price_a / price_b)as price_a_b,
sales_a * 2 as s_sales_a
FROM
chapter7
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result:

1.2 Divisible and mod operations

SELECT 7 DIV 2
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result:

SELECT 7 % 2
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SELECT 7 MOD 2
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result:

1.3 Null-related operations

Null Evaluates to any number, resulting in null

SELECT
    1 + NULL,
    1-NULL,
    1 * NULL,
    1 / NULL
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result:

2. Comparison operation

Common comparison operators

The operator	meaning
>	Is greater than
<	Less than
=	Is equal to the
> =	Greater than or equal to
< =	Less than or equal to
! =	Is not equal to
<>	Is not equal to
between A and B	[A, B]
is null	A null value
is not null	The null value

2.1 Comparison between columns

SELECT id, sales_A, sales_B, sales_A > sales_B as "> ", sales_A < sales_B as" < ", sales_A = sales_B as "= ", sales_A! = sales_B as "not equal ", sales_A is null as" null ", sales_A is not null as "non-null" FROM chapter7Copy the code

result:

Here’s an illustration of the comparison operation. Returns 1 if the comparison is true, 0 otherwise

2.2 Condition Screening

SELECT
id,
sales_a
FROM
chapter7
WHERE sales_a BETWEEN 14 AND 18
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result: