构建自定义PostgreSQL MCP服务器
中级
这是一个Building Blocks, AI领域的自动化工作流，包含 15 个节点。主要使用 Switch, Postgres, PostgresTool, McpTrigger, ToolWorkflow 等节点，结合人工智能技术实现智能自动化。 构建自定义PostgreSQL MCP服务器
前置要求
- •PostgreSQL 数据库连接信息
工作流预览
可视化展示节点连接关系，支持缩放和平移
导出工作流
复制以下 JSON 配置到 n8n 导入，即可使用此工作流
{
"meta": {
"instanceId": "408f9fb9940c3cb18ffdef0e0150fe342d6e655c3a9fac21f0f644e8bedabcd9",
"templateCredsSetupCompleted": true
},
"nodes": [
{
"id": "0c49141e-128c-424e-afdf-ea131b7a3dd8",
"name": "获取表结构",
"type": "n8n-nodes-base.postgresTool",
"position": [
-460,
220
],
"parameters": {
"query": "SELECT column_name, data_type FROM information_schema.columns WHERE table_name = $1",
"options": {
"queryReplacement": "={{ $fromAI('tableName', 'The name of the table.') }}"
},
"operation": "executeQuery",
"descriptionType": "manual",
"toolDescription": "Read a table's schema."
},
"credentials": {
"postgres": {
"id": "elRn5sxKOfCdlEs6",
"name": "Postgres account"
}
},
"typeVersion": 2.6
},
{
"id": "8ffeefb9-357c-41bc-8239-0c07c706be97",
"name": "列出表",
"type": "n8n-nodes-base.postgresTool",
"position": [
-340,
300
],
"parameters": {
"query": "SELECT table_name FROM information_schema.tables WHERE table_schema = 'public'",
"options": {},
"operation": "executeQuery",
"descriptionType": "manual",
"toolDescription": "List all available tables."
},
"credentials": {
"postgres": {
"id": "elRn5sxKOfCdlEs6",
"name": "Postgres account"
}
},
"typeVersion": 2.6
},
{
"id": "efcf7ff3-976e-448a-9d47-47a98f3b0fcb",
"name": "当被其他工作流执行时",
"type": "n8n-nodes-base.executeWorkflowTrigger",
"position": [
280,
200
],
"parameters": {
"workflowInputs": {
"values": [
{
"name": "operation"
},
{
"name": "tableName"
},
{
"name": "values",
"type": "object"
},
{
"name": "where",
"type": "object"
}
]
}
},
"typeVersion": 1.1
},
{
"id": "abd292d7-fc2b-4e98-a474-b50e44d16b6c",
"name": "创建表记录",
"type": "@n8n/n8n-nodes-langchain.toolWorkflow",
"position": [
-240,
400
],
"parameters": {
"name": "CreateTableRows",
"workflowId": {
"__rl": true,
"mode": "id",
"value": "={{ $workflow.id }}"
},
"description": "调用此工具在数据库中创建一行。",
"workflowInputs": {
"value": {
"where": "={{ {} }}",
"values": "={{ /*n8n-auto-generated-fromAI-override*/ $fromAI('values', `An object of key-value pair where key represents the column name.`, 'string') }}",
"operation": "insert",
"tableName": "={{ /*n8n-auto-generated-fromAI-override*/ $fromAI('tableName', `Name of table to update`, 'string') }}"
},
"schema": [
{
"id": "operation",
"type": "string",
"display": true,
"removed": false,
"required": false,
"displayName": "operation",
"defaultMatch": false,
"canBeUsedToMatch": true
},
{
"id": "tableName",
"type": "string",
"display": true,
"removed": false,
"required": false,
"displayName": "tableName",
"defaultMatch": false,
"canBeUsedToMatch": true
},
{
"id": "values",
"type": "object",
"display": true,
"removed": false,
"required": false,
"displayName": "values",
"defaultMatch": false,
"canBeUsedToMatch": true
},
{
"id": "where",
"type": "object",
"display": true,
"removed": false,
"required": false,
"displayName": "where",
"defaultMatch": false,
"canBeUsedToMatch": true
}
],
"mappingMode": "defineBelow",
"matchingColumns": [],
"attemptToConvertTypes": false,
"convertFieldsToString": false
}
},
"typeVersion": 2.1
},
{
"id": "4a71d42a-99a5-489e-b449-09c3c5081505",
"name": "读取表记录",
"type": "n8n-nodes-base.postgres",
"position": [
760,
0
],
"parameters": {
"query": "SELECT * FROM {{ $json.tableName }}\n{{ $json.where && Object.keys($json.where).length > 0\n ? `WHERE ` + Object.keys($json.where).map((key,idx) => `${key} = $${idx+1}`).join(' AND ')\n : ''\n}}",
"options": {
"queryReplacement": "={{ Object.values($json.where).join(',') }}"
},
"operation": "executeQuery"
},
"credentials": {
"postgres": {
"id": "elRn5sxKOfCdlEs6",
"name": "Postgres account"
}
},
"typeVersion": 2.6,
"alwaysOutputData": true
},
{
"id": "bdc60aa8-9ab1-4bbd-8b9e-89c968d54043",
"name": "Operation",
"type": "n8n-nodes-base.switch",
"position": [
460,
200
],
"parameters": {
"rules": {
"values": [
{
"outputKey": "READ",
"conditions": {
"options": {
"version": 2,
"leftValue": "",
"caseSensitive": true,
"typeValidation": "strict"
},
"combinator": "and",
"conditions": [
{
"id": "81b134bc-d671-4493-b3ad-8df9be3f49a6",
"operator": {
"type": "string",
"operation": "equals"
},
"leftValue": "={{ $json.operation }}",
"rightValue": "read"
}
]
},
"renameOutput": true
},
{
"outputKey": "INSERT",
"conditions": {
"options": {
"version": 2,
"leftValue": "",
"caseSensitive": true,
"typeValidation": "strict"
},
"combinator": "and",
"conditions": [
{
"id": "8d57914f-6587-4fb3-88e0-aa1de6ba56c1",
"operator": {
"name": "filter.operator.equals",
"type": "string",
"operation": "equals"
},
"leftValue": "={{ $json.operation }}",
"rightValue": "insert"
}
]
},
"renameOutput": true
},
{
"outputKey": "UPDATE",
"conditions": {
"options": {
"version": 2,
"leftValue": "",
"caseSensitive": true,
"typeValidation": "strict"
},
"combinator": "and",
"conditions": [
{
"id": "7c38f238-213a-46ec-aefe-22e0bcb8dffc",
"operator": {
"name": "filter.operator.equals",
"type": "string",
"operation": "equals"
},
"leftValue": "={{ $json.operation }}",
"rightValue": "update"
}
]
},
"renameOutput": true
}
]
},
"options": {}
},
"typeVersion": 3.2
},
{
"id": "cdb5b556-3638-4fa5-94c6-bff0c03f6c89",
"name": "更新表记录",
"type": "n8n-nodes-base.postgres",
"position": [
760,
400
],
"parameters": {
"query": "UPDATE {{ $json.tableName }}\nSET\n {{ Object.keys($json.values)\n .map((key,idx) => `${key} = $${idx+1}`)\n .join(',')\n}}\nWHERE\n {{ Object.keys($json.where)\n .map((key,idx) => `${key} = $${idx+Object.keys($json.values).length+1}`)\n .join(' AND ')\n}}",
"options": {
"queryReplacement": "={{ Object.values($json.values).join(',') }},{{ Object.values($json.where).join(',') }}"
},
"operation": "executeQuery"
},
"credentials": {
"postgres": {
"id": "elRn5sxKOfCdlEs6",
"name": "Postgres account"
}
},
"typeVersion": 2.6
},
{
"id": "9263fc78-321e-4c83-90d3-890dd87d6aed",
"name": "更新表记录",
"type": "@n8n/n8n-nodes-langchain.toolWorkflow",
"position": [
-100,
320
],
"parameters": {
"name": "UpdateTableRows",
"workflowId": {
"__rl": true,
"mode": "id",
"value": "={{ $workflow.id }}"
},
"description": "调用此工具在数据库中创建一行。",
"workflowInputs": {
"value": {
"where": "={{ /*n8n-auto-generated-fromAI-override*/ $fromAI('where', `An object of key-value pair where key represents the column name.`, 'string') }}",
"values": "={{ /*n8n-auto-generated-fromAI-override*/ $fromAI('values', `An object of key-value pair where key represents the column name.`, 'string') }}",
"operation": "=update",
"tableName": "={{ /*n8n-auto-generated-fromAI-override*/ $fromAI('tableName', `Table to update`, 'string') }}"
},
"schema": [
{
"id": "operation",
"type": "string",
"display": true,
"removed": false,
"required": false,
"displayName": "operation",
"defaultMatch": false,
"canBeUsedToMatch": true
},
{
"id": "tableName",
"type": "string",
"display": true,
"removed": false,
"required": false,
"displayName": "tableName",
"defaultMatch": false,
"canBeUsedToMatch": true
},
{
"id": "values",
"type": "object",
"display": true,
"removed": false,
"required": false,
"displayName": "values",
"defaultMatch": false,
"canBeUsedToMatch": true
},
{
"id": "where",
"type": "object",
"display": true,
"removed": false,
"required": false,
"displayName": "where",
"defaultMatch": false,
"canBeUsedToMatch": true
}
],
"mappingMode": "defineBelow",
"matchingColumns": [],
"attemptToConvertTypes": false,
"convertFieldsToString": false
}
},
"typeVersion": 2.1
},
{
"id": "dd7e28fb-b2c7-4084-bc9b-9aa3e0187682",
"name": "创建表记录",
"type": "n8n-nodes-base.postgres",
"position": [
760,
200
],
"parameters": {
"query": "INSERT INTO {{ $json.tableName }}\n ({{ Object.keys($json.values).join(',') }})\nVALUES\n ({{ Object.keys($json.values).map((_,idx) => `$${idx+1}`).join(',') }})",
"options": {
"queryReplacement": "={{ Object.values($json.values).join(',') }}"
},
"operation": "executeQuery"
},
"credentials": {
"postgres": {
"id": "elRn5sxKOfCdlEs6",
"name": "Postgres account"
}
},
"typeVersion": 2.6
},
{
"id": "324503c0-117b-45ec-97dd-7074eb1db22e",
"name": "读取表行",
"type": "@n8n/n8n-nodes-langchain.toolWorkflow",
"position": [
20,
240
],
"parameters": {
"name": "ReadTableRows",
"workflowId": {
"__rl": true,
"mode": "id",
"value": "={{ $workflow.id }}"
},
"description": "调用此工具读取数据库中的一行。",
"workflowInputs": {
"value": {
"where": "={{ /*n8n-auto-generated-fromAI-override*/ $fromAI('where', `An object of key-value pair where key represents the column name.`, 'string') }}",
"values": "{}",
"operation": "read",
"tableName": "={{ /*n8n-auto-generated-fromAI-override*/ $fromAI('tableName', ``, 'string') }}"
},
"schema": [
{
"id": "operation",
"type": "string",
"display": true,
"removed": false,
"required": false,
"displayName": "operation",
"defaultMatch": false,
"canBeUsedToMatch": true
},
{
"id": "tableName",
"type": "string",
"display": true,
"removed": false,
"required": false,
"displayName": "tableName",
"defaultMatch": false,
"canBeUsedToMatch": true
},
{
"id": "values",
"type": "object",
"display": true,
"removed": false,
"required": false,
"displayName": "values",
"defaultMatch": false,
"canBeUsedToMatch": true
},
{
"id": "where",
"type": "object",
"display": true,
"removed": false,
"required": false,
"displayName": "where",
"defaultMatch": false,
"canBeUsedToMatch": true
}
],
"mappingMode": "defineBelow",
"matchingColumns": [],
"attemptToConvertTypes": false,
"convertFieldsToString": false
}
},
"typeVersion": 2.1
},
{
"id": "9cf39ca3-b704-49ce-b6e2-db2703c4acad",
"name": "便签",
"type": "n8n-nodes-base.stickyNote",
"position": [
-520,
-120
],
"parameters": {
"color": 7,
"width": 680,
"height": 660,
"content": "## 1. 设置 MCP 服务器触发器"
},
"typeVersion": 1
},
{
"id": "ac3d9b98-8f1e-4abd-972c-1725aac1ad1e",
"name": "PostgreSQL MCP 服务器",
"type": "@n8n/n8n-nodes-langchain.mcpTrigger",
"position": [
-340,
20
],
"webhookId": "a5fd7047-e31b-4c0d-bd68-c36072c3da0d",
"parameters": {
"path": "a5fd7047-e31b-4c0d-bd68-c36072c3da0d"
},
"typeVersion": 1
},
{
"id": "416a09d5-c327-410d-b951-a2d08402c6fe",
"name": "便签1",
"type": "n8n-nodes-base.stickyNote",
"position": [
180,
-120
],
"parameters": {
"color": 7,
"width": 820,
"height": 720,
"content": "## 2. 通过防止原始 SQL 语句保持安全"
},
"typeVersion": 1
},
{
"id": "0187fb3f-4c31-461d-84e9-4a4a0bf4188d",
"name": "便签2",
"type": "n8n-nodes-base.stickyNote",
"position": [
-1000,
-560
],
"parameters": {
"width": 440,
"height": 1320,
"content": "## 试试看！"
},
"typeVersion": 1
},
{
"id": "bc4e427f-f6fd-4243-844a-8edf2dc1a0e9",
"name": "便签3",
"type": "n8n-nodes-base.stickyNote",
"position": [
-520,
-240
],
"parameters": {
"color": 5,
"width": 380,
"height": 100,
"content": "### 始终验证您的服务器！"
},
"typeVersion": 1
}
],
"pinData": {},
"connections": {
"Operation": {
"main": [
[
{
"node": "ReadTableRecord",
"type": "main",
"index": 0
}
],
[
{
"node": "CreateTableRecord",
"type": "main",
"index": 0
}
],
[
{
"node": "UpdateTableRecord",
"type": "main",
"index": 0
}
]
]
},
"ListTables": {
"ai_tool": [
[
{
"node": "PostgreSQL MCP Server",
"type": "ai_tool",
"index": 0
}
]
]
},
"ReadTableRows": {
"ai_tool": [
[
{
"node": "PostgreSQL MCP Server",
"type": "ai_tool",
"index": 0
}
]
]
},
"GetTableSchema": {
"ai_tool": [
[
{
"node": "PostgreSQL MCP Server",
"type": "ai_tool",
"index": 0
}
]
]
},
"ReadTableRecord": {
"main": [
[]
]
},
"CreateTableRecords": {
"ai_tool": [
[
{
"node": "PostgreSQL MCP Server",
"type": "ai_tool",
"index": 0
}
]
]
},
"UpdateTableRecords": {
"ai_tool": [
[
{
"node": "PostgreSQL MCP Server",
"type": "ai_tool",
"index": 0
}
]
]
},
"When Executed by Another Workflow": {
"main": [
[
{
"node": "Operation",
"type": "main",
"index": 0
}
]
]
}
}
}常见问题
如何使用这个工作流？
复制上方的 JSON 配置代码，在您的 n8n 实例中创建新工作流并选择「从 JSON 导入」，粘贴配置后根据需要修改凭证设置即可。
这个工作流适合什么场景？
中级 - 构建模块, 人工智能
需要付费吗？
本工作流完全免费，您可以直接导入使用。但请注意，工作流中使用的第三方服务（如 OpenAI API）可能需要您自行付费。
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工作流信息
难度等级
中级
节点数量15
分类2
节点类型7
作者
Jimleuk
@jimleukFreelance consultant based in the UK specialising in AI-powered automations. I work with select clients tackling their most challenging projects. For business enquiries, send me an email at hello@jimle.uk LinkedIn: https://www.linkedin.com/in/jimleuk/ X/Twitter: https://x.com/jimle_uk
外部链接
在 n8n.io 查看 →
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