# 解析器
解析器主用于解析Sql语句，以供 分库中间件做分库决策及对结果合并计算
# 简介
为了降低开发难度，Dce以\dce\db\query\builder\StatementAbstract对象作为分库决策判断条件。作者本想通过这个取巧，舍弃对原生语句分库查询的支持，以绕开Sql语句解析器的开发需求。但后面发现做合并计算时需要提取聚合函数，这个需求无法绕开，或者为了绕开需要大大增加Query对象的使用成本。所以没办法，作者最终还是编写了Sql解析器。但为了偷懒，只编写了对影响聚合计算的部分的解析器，所以分库查询还是只支持对象式的查询，后续可能会完善解析器以支持全语句解析，但那都是后话了。
本模块文件较多，并且你基本不会直接用到，所以不展开细讲，有兴趣者可自行查看源代码了解。
# \dce\sharding\parser\mysql\list\MysqlColumnParser
# ::build()
解析SELECT语句的COLUMN部分
参数
string $statement待解析语句int & $offset = 0起始解析偏移位置
返回
self示例
$sql = "distinct case f1 when 1 then 2 else 0 end, sum (case f2 when 2 then 3 when 4 then 5 else 1 end) a1,
`db1`.t1.`field1` as f1, t2 . field2 `f2`, field3 , 32.5,1,
2 field2, 'aaa' as field, 'aa,ass55,5,5,\'fdfsd' g5,
sum(`t1`.`field1`) as f1, max(if_null(field2, 0)) as f2, count(distinct field3)";
$parser = MysqlColumnParser::build($sql);
test($parser->toArray());
/*
1-1 array(4) {
["type"] => string(4) "list"
["class"] => string(6) "column"
["modifiers"] => array(1) {
[0] => string(8) "distinct"
}
["columns"] => array(13) {
[0] => array(4) {
["type"] => string(9) "statement"
["statement"] => string(6) "column"
["field"] => array(5) {
["type"] => string(9) "statement"
["statement"] => string(4) "case"
["case"] => array(4) {
["type"] => string(5) "field"
["field"] => string(2) "f1"
["table"] => NULL
["db"] => NULL
}
["when"] => array(1) {
[0] => array(4) {
["type"] => string(9) "statement"
["statement"] => string(4) "when"
["when"] => array(2) {
["type"] => string(5) "value"
["value"] => float(1)
}
["then"] => array(2) {
["type"] => string(5) "value"
["value"] => float(2)
}
}
}
["else"] => array(2) {
["type"] => string(5) "value"
["value"] => float(0)
}
}
["alias"] => NULL
}
[1] => array(4) {
["type"] => string(9) "statement"
["statement"] => string(6) "column"
["field"] => array(4) {
["type"] => string(8) "function"
["name"] => string(3) "SUM"
["modifiers"] => NULL
["arguments"] => array(1) {
[0] => array(5) {
["type"] => string(9) "statement"
["statement"] => string(4) "case"
["case"] => array(4) {
["type"] => string(5) "field"
["field"] => string(2) "f2"
["table"] => NULL
["db"] => NULL
}
["when"] => array(2) {
[0] => array(4) {
["type"] => string(9) "statement"
["statement"] => string(4) "when"
["when"] => array(2) {
["type"] => string(5) "value"
["value"] => float(2)
}
["then"] => array(2) {
["type"] => string(5) "value"
["value"] => float(3)
}
}
[1] => array(4) {
["type"] => string(9) "statement"
["statement"] => string(4) "when"
["when"] => array(2) {
["type"] => string(5) "value"
["value"] => float(4)
}
["then"] => array(2) {
["type"] => string(5) "value"
["value"] => float(5)
}
}
}
["else"] => array(2) {
["type"] => string(5) "value"
["value"] => float(1)
}
}
}
}
["alias"] => string(2) "a1"
}
[2] => array(4) {
["type"] => string(9) "statement"
["statement"] => string(6) "column"
["field"] => array(4) {
["type"] => string(5) "field"
["field"] => string(6) "field1"
["table"] => string(2) "t1"
["db"] => string(3) "db1"
}
["alias"] => string(2) "f1"
}
[3] => array(4) {
["type"] => string(9) "statement"
["statement"] => string(6) "column"
["field"] => array(4) {
["type"] => string(5) "field"
["field"] => string(6) "field2"
["table"] => string(2) "t2"
["db"] => NULL
}
["alias"] => string(2) "f2"
}
[4] => array(4) {
["type"] => string(9) "statement"
["statement"] => string(6) "column"
["field"] => array(4) {
["type"] => string(5) "field"
["field"] => string(6) "field3"
["table"] => NULL
["db"] => NULL
}
["alias"] => NULL
}
[5] => array(4) {
["type"] => string(9) "statement"
["statement"] => string(6) "column"
["field"] => array(2) {
["type"] => string(5) "value"
["value"] => float(32.5)
}
["alias"] => NULL
}
[6] => array(4) {
["type"] => string(9) "statement"
["statement"] => string(6) "column"
["field"] => array(2) {
["type"] => string(5) "value"
["value"] => float(1)
}
["alias"] => NULL
}
[7] => array(4) {
["type"] => string(9) "statement"
["statement"] => string(6) "column"
["field"] => array(2) {
["type"] => string(5) "value"
["value"] => float(2)
}
["alias"] => string(6) "field2"
}
[8] => array(4) {
["type"] => string(9) "statement"
["statement"] => string(6) "column"
["field"] => array(2) {
["type"] => string(5) "value"
["value"] => string(3) "aaa"
}
["alias"] => string(5) "field"
}
[9] => array(4) {
["type"] => string(9) "statement"
["statement"] => string(6) "column"
["field"] => array(2) {
["type"] => string(5) "value"
["value"] => string(20) "aa,ass55,5,5,\'fdfsd"
}
["alias"] => string(2) "g5"
}
[10] => array(4) {
["type"] => string(9) "statement"
["statement"] => string(6) "column"
["field"] => array(4) {
["type"] => string(8) "function"
["name"] => string(3) "SUM"
["modifiers"] => NULL
["arguments"] => array(1) {
[0] => array(4) {
["type"] => string(5) "field"
["field"] => string(6) "field1"
["table"] => string(2) "t1"
["db"] => NULL
}
}
}
["alias"] => string(2) "f1"
}
[11] => array(4) {
["type"] => string(9) "statement"
["statement"] => string(6) "column"
["field"] => array(4) {
["type"] => string(8) "function"
["name"] => string(3) "MAX"
["modifiers"] => NULL
["arguments"] => array(1) {
[0] => array(4) {
["type"] => string(8) "function"
["name"] => string(7) "IF_NULL"
["modifiers"] => NULL
["arguments"] => array(2) {
[0] => array(4) {
["type"] => string(5) "field"
["field"] => string(6) "field2"
["table"] => NULL
["db"] => NULL
}
[1] => array(2) {
["type"] => string(5) "value"
["value"] => float(0)
}
}
}
}
}
["alias"] => string(2) "f2"
}
[12] => array(4) {
["type"] => string(9) "statement"
["statement"] => string(6) "column"
["field"] => array(4) {
["type"] => string(8) "function"
["name"] => string(5) "COUNT"
["modifiers"] => array(1) {
[0] => string(8) "distinct"
}
["arguments"] => array(1) {
[0] => array(4) {
["type"] => string(5) "field"
["field"] => string(6) "field3"
["table"] => NULL
["db"] => NULL
}
}
}
["alias"] => NULL
}
}
}
*/
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
# 注意
WARNING
解析器支持的语法已基本在上述示例中包括，尚不支持对计算运算符、逻辑运算符、判断运算符等的解析。如果你的Sql的SELECT COLUMN部分包含有不支持的语法，将会抛出异常或者导致结果错误。对于这些不支持的语法，你可以在取出结果后自行编程实现。作者会评估这些语法的重要性及研发难易度，陆续的支持完善。