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Q&A Why would excluding records by creating a temporary table of their primary keys be faster than simply excluding by value?

I have two tables with millions of records. Every so often I need to join them and exclude just a handful of records where a bit(1) column is set to 1 instead of 0. I can do it with either, WHERE ...

2 answers · posted 4y ago by Charlie Brumbaugh‭ · edited 4y ago by Alexei‭

Question mysql sql notin query-performance

#5: Post edited by

Alexei‭ · 2020-10-19T05:16:37Z (about 4 years ago)
added relevant tags

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I have two tables with millions of records. Every so often I need to join them and exclude just a handful of records where a bit(1) column is set to 1 instead of 0.
I can do it with either,
```sql
WHERE is_excluded !=1
```
or
```sql
WHERE example_table.pk NOT IN
(
SELECT pk FROM(
SELECT pk FROM
example_table
WHERE is_excluded =1)
AS t)
```
For example
```
UPDATE example_table
SET textfield = 'X'
WHERE textfield = 'Y'
and pk not in (SELECT pk FROM (SELECT pk FROM example_table WHERE do_not_touch =1)as t) ;
```
is faster than
```
UPDATE example_table
SET textfield = 'X'
WHERE textfield = 'Y'
and do_not_touch !=1
```
The second way is sometimes way faster, even though it takes much longer to write out.
Why would the second way be faster?

I have two tables with millions of records. Every so often I need to join them and exclude just a handful of records where a bit(1) column is set to 1 instead of 0.
I can do it with either,
```sql
WHERE is_excluded !=1
```
or
```sql
WHERE example_table.pk NOT IN
(
SELECT pk FROM(
SELECT pk FROM
example_table
WHERE is_excluded =1)
AS t)
```
For example
```
UPDATE example_table
SET textfield = 'X'
WHERE textfield = 'Y'
and pk not in (SELECT pk FROM (SELECT pk FROM example_table WHERE do_not_touch =1)as t) ;
```
is faster than
```
UPDATE example_table
SET textfield = 'X'
WHERE textfield = 'Y'
and do_not_touch !=1
```
The second way is sometimes way faster, even though it takes much longer to write out.
Why would the second way be faster?

#4: Post edited by

Charlie Brumbaugh‭ · 2020-08-07T18:24:28Z (over 4 years ago)

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I have two tables with millions of records. Every so often I need to join them and exclude just a handful of records where a bit(1) column is set to 1 instead of 0.
I can do it with either,
```sql
WHERE is_excluded !=1
```
or
```sql
WHERE example_table.pk NOT IN
(
SELECT pk FROM(
SELECT pk FROM
example_table
WHERE is_excluded =1)
AS t)
```
The second way is sometimes way faster, even though it takes much longer to write out.
Why would the second way be faster?

I have two tables with millions of records. Every so often I need to join them and exclude just a handful of records where a bit(1) column is set to 1 instead of 0.
I can do it with either,
```sql
WHERE is_excluded !=1
```
or
```sql
WHERE example_table.pk NOT IN
(
SELECT pk FROM(
SELECT pk FROM
example_table
WHERE is_excluded =1)
AS t)
```
For example
```
UPDATE example_table
SET textfield = 'X'
WHERE textfield = 'Y'
and pk not in (SELECT pk FROM (SELECT pk FROM example_table WHERE do_not_touch =1)as t) ;
```
is faster than
```
UPDATE example_table
SET textfield = 'X'
WHERE textfield = 'Y'
and do_not_touch !=1
```
The second way is sometimes way faster, even though it takes much longer to write out.
Why would the second way be faster?

#3: Post edited by

ArtOfCode‭ · 2020-08-07T16:35:47Z (over 4 years ago)
tags, syntax highlighting hints

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I have two tables with millions of records. Every so often I need to join them and exclude just a handful of records where a bit(1) column is set to 1 instead of 0.
I can do it with either,
~~```~~
WHERE is_excluded !=1
```
or
~~```~~
WHERE example_table.pk NOT IN
(
SELECT pk FROM(
SELECT pk FROM
example_table
WHERE is_excluded =1)
AS t)
```
The second way is sometimes way faster, even though it takes much longer to write out.
Why would the second way be faster?

I have two tables with millions of records. Every so often I need to join them and exclude just a handful of records where a bit(1) column is set to 1 instead of 0.
I can do it with either,
```sql
WHERE is_excluded !=1
```
or
```sql
WHERE example_table.pk NOT IN
(
SELECT pk FROM(
SELECT pk FROM
example_table
WHERE is_excluded =1)
AS t)
```
The second way is sometimes way faster, even though it takes much longer to write out.
Why would the second way be faster?

#2: Post edited by

Charlie Brumbaugh‭ · 2020-08-07T15:24:27Z (over 4 years ago)

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~~I have two tables with millions of records. Every so often I need to join them and exclude just handful of records where a bit(1) column is set to 1 instead of 0.~~
I can do it with either,
```
WHERE is_excluded !=1
```
or
```
WHERE example_table.pk NOT IN
(
SELECT pk FROM(
SELECT pk FROM
example_table
WHERE is_excluded =1)
AS t)
```
The second way is sometimes way faster, even though it takes much longer to write out.
Why would the second way be faster?

I have two tables with millions of records. Every so often I need to join them and exclude just a handful of records where a bit(1) column is set to 1 instead of 0.
I can do it with either,
```
WHERE is_excluded !=1
```
or
```
WHERE example_table.pk NOT IN
(
SELECT pk FROM(
SELECT pk FROM
example_table
WHERE is_excluded =1)
AS t)
```
The second way is sometimes way faster, even though it takes much longer to write out.
Why would the second way be faster?

#1: Initial revision by

Charlie Brumbaugh‭ · 2020-08-07T15:13:08Z (over 4 years ago)

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Why would excluding records by creating a temporary table of their primary keys be faster than simply excluding by value?

I have two tables with millions of records. Every so often I need to join them and  exclude just handful of records where a bit(1) column is set to 1 instead of 0.

I can do it with either,

```
WHERE is_excluded !=1
```

or

```
WHERE example_table.pk NOT IN
(
  SELECT pk FROM(
    SELECT pk FROM
    example_table
    WHERE is_excluded =1) 
AS t)
```

The second way is sometimes way faster, even though it takes much longer to write out.

Why would the second way be faster?

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