MySQL database table field replication

Copy fields across different tables:

The SQL query statement uses the JOIN operation to copy the value from Field 1 to Field 2.

For example, suppose you have two tables; one of them istable1,the other one istable2,amongtable1Include Fieldfield1和field2,buttable2Include Fieldfield1和field2You can use the following SQL query statement to:table1Infield1Value copied totable2Infield2In the field:

SELECT table2.field2  
FROM table1  
INNER JOIN table2  
ON table1.field1 = table2.field1;

In the above query statement,INNER JOINThe operation connects two tables and willtable1Infield1Field andtable2Infield1Field matching. Then, you can use it.table2.field2Retrieve from the fieldtable2Return the corresponding value as the result.

If you need to retain the query resultstable1和table2The original fields in the query statement can be used.SELECTSome parts have been modified.SELECT *This allows you to include all fields.

Field replication within the same table:

If you want to replace the values of two fields within the same table, you can use SQL. UPDATE Implement via operation.

For example, suppose you have something namedtable1Table containing fieldsfield1和field2You can use the following SQL query statement to:table1Infield1The value is replaced byfield2Value:

UPDATE table1    
SET field2 = field1;

In the above query statement,UPDATEOperation will be performed.table1All rows in the table are updated to "will".field1The value is replaced byfield2Value. You can include this in your query statement.table1Replace the placeholder with the actual table name, then run the query to update the data in the table.

If you need to retain the original fields in the query results, you can modify the query statement accordingly. UPDATE Some parts have been modified. UPDATE * FROM table1 SET field2 = field1 Just done.