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This article introduces the relevant knowledge of "what is the principle of database implementation plan". In the operation of actual cases, many people will encounter such a dilemma. Next, let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Implement the Plan Review principles:

The step of Operation column is a tree, ID=0 is the root node of the tree, a root node can have multiple child nodes, and expansion is from top to bottom, left to right, indicating the process of oracle reading SQL, while the real SQL execution order is to start from the parent node to find, there are child nodes to execute the child node first, there are multiple child nodes to execute the first from top to bottom, and the child nodes finish all the execution before executing the parent node.

Looking from top to bottom, when you see the first juxtaposed node, pause to look down, and the execution order of the upper node must be greater than the following execution order (juxtaposed uplink), then the upper node takes precedence over the upper node, according to the above principles:

1. If the node has a child node, continue to look down and indent to the right, find the juxtaposition node, and give priority to the upper node if there is a juxtaposition node, until a node has no juxtaposition node, and the node executes first.

2. If the node no longer has a child node at this time, the node executes first.

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