SQL deletes duplicate rows (ALL or DISTINCT)

The "ALL" or "DISTINCT" option is used in the SELECT statement for deleting duplicate rows to display ALL rows that meet the conditions in the table or delete duplicate data rows in the table. The default value is "ALL. When the DISTINCT option is used, only one row is retained for all duplicate data rows in the result set returned by the SELECT statement.

SQL deletes duplicate rows (all or distinct)
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The "all" or "distinct" option is used in the select statement for deleting duplicate rows to display all rows that meet the conditions in the table or delete duplicate data rows in the table. The default value is "all. When the distinct option is used, only one row is retained for all duplicate data rows in the result set returned by the select statement.

We can also use it to remove duplicate data.

Merge two tables to remove duplicate data (mainly Table 2 data). We will get the following table:

A B

A 1

B 0

C 0

D 0

E 4

Select a, B from table 1 where a not in (select a from table 2)

Union

Select a, B from table 2

// Distinct syntax

Select distinct "column name" from "table name"

// SQL union all syntax

Select column_name (s) from table_name1 union all select column_name (s) from table_name2