mysql - set two fields as primary key -

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मैं निम्नलिखित एसक्यूएल क्वेरी को दिखाता हूं। 

  ALTER TABLE dbo.YourTableNameHere जोड़ें CONSTRAINT PK_YourTableNameHere प्राथमिक कुंजी (मद_आईडी, खरीद_आईडी)

"PK_YourTableNameHere" से इसका क्या अर्थ है? क्या यह टेबल की वर्तमान प्राथमिक कुंजी है?

प्राथमिक कुंजी बाधा का नाम वैकल्पिक है (देखें)।
इसे आप क्या कहते हैं या इसे पूरी तरह से न छोड़ें - इसमें कोई फर्क नहीं पड़ता।


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