Table 1. did not add a primary key, its data disorderly placed on disk storage, line by line arranged very neatly.
2. The addition of a table's primary key, and not be called "table." If the primary key to the table, then the table is stored on disk structure is transformed by the alignment of the structure it became a tree, and was "balanced tree" structure, in other words, the entire table becomes an index. Yes, again, the whole table turned into an index, the so-called "clustered index." This is why a table can have only one primary key, a table can have only a "clustered index", because the role of the primary key is to convert the "table" of the data format to "index (balanced tree)" format placement.
matplotlib.pyplot AS PLT Import
plt.rcParams [www.yongyunzhuce.cn'font.sans-serif '] = [' SimHei ']
x_data = [2011,2012,2013,2014,2015,2016,2017]
y_data = [WWW 58000,60200,63000,71000,84000,90500,107000 .zhuyngyule.cn]
plt.xticks (x_data, [ '2011 Nian', '2012', '2013', '2014', '2015', '2016', '2017'])
plt.yticks (y_data)
plt.plot (x_data, www.feiyuptzc.cn_data)
plt.show (www.xingchenylzc.cn)
was as follows:
in some cases, since the data desensitization need, we do not display scale, so you can also write:
plt.xticks (www.shentuylgw.cn_data, [baishiyl2zc.cn])
plt.yticks (www.tianjipp3zc.cn_data, [www.yunsheng-pt.com])
this show out of the graphics as follows:
in fact, we have Genghen operation, directly off axis:
plt.axis ( "OFF" the WWW.jintianxuesha.com)
were as follows:
range setting
We can also set the range of the coordinate axes, as follows:
Import matplotlib.pyplot AS PLT
plt.rcParams [ 'font.sans-serif'www.lecaixuanzc.cn] = [www.feishenbo.cn'SimHei']
x_data = [ 2011,2012,2013,2014,2015,2016,2017]
y_data = [58000,60200,63000,71000,84000,90500,107000]
plt.xlim (2011, 2020)
plt.ylim (50000, 90000)
plt.plot (x_data, y_data)
3. a plurality of fields plus a conventional table index, it will appear a plurality of separate index structure data field will be copy out, for generating an index, the leaf node ID is the primary key, which It is a non-clustered index., and the following is a primary key index structure of a conventional three
4. The primary key to check the leaf node is the data line
The index field to check by another, then the leaf node is the primary key ID, and then check again according to the master key, the clustered index (primary key) is the only path to where the real data
7. One exception may not use the clustered index will be able to check out the required data, such non-mainstream approach called "covering index" inquiry, which is usually said composite index or a multiple-field index query
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