Method 1 (Early Transaction):
procedures:

start transaction
 select * from tempa;
 insert into tempb(id,name,create_time)values(1,"tom","2025-03-27");
commit transaction

Lock Duration: From INSERT to COMMIT

Method 2 (Late Transaction):
procedures:

  select * from tempa;
start transaction
  insert into tempb(id,name,create_time)values(1,"tom","2025-03-27");
commit transaction

Lock Duration: Also covers INSERT to COMMIT。  But Transaction Lifetime is  shorter than Method 1

Critical Insight:

Both methods hold locks for the same duration in the example, because:

Regular SELECT (without explicit locking clauses) doesn't acquire locks in MySQL's default（unless SERIALIZABLE  ） isolation level
True lock contention occurs only during the INSERT operation
============knowledge derivation====================
Practical Advice
Use SELECT ... FOR UPDATE if you need to lock rows early:

START TRANSACTION;
SELECT * FROM tempa FOR UPDATE; -- Explicit lock acquired here
INSERT INTO tempb ... ; 
COMMIT; 

→ In this scenario, Method 1 would indeed extend lock duration, making Method 2 more optimal."